Llanarth's strikes came from Daniel Wheeler (2), and Tom Bodham, Jamie Edwards, Gavin Phillips and Michael Morgan all scored one apiece.
Llanarth's man of the match was Jamie Edwards.
Second placed side Raglan had a 2-1 home win over Usk Town. The sides were level 0-0 at half-time and with three minutes left to play the sides appeared to be heading for a 1-1 draw.
However, Raglan were awarded a penalty in the 87th minute and Chris Tyler scored from the spot.
Man of the match for Raglan was Chris Tyler.
Man of the match for Usk Town was Will Barton.
Llanfoist were hoping to lift themselves off the bottom position going into their local derby home match against Pandy, but it was the visitors who established a 0-5 half time lead before going on to lay Llanfoist to waste 1-9.
Man of the match Chris Morgan scored an impressive five goals for Pandy, Kirk Morgan bagged a brace, and Jason Osborne and Leyton Davies chipped in with one apiece.
Llanfoist's consolation goal was scored by their man of the match Gareth Williams.
Current Division One leaders Govilon continue to lead the way at the top following their storming 13-0 home thrashing over Race.
Man of the match Jamie Wilkins scored a hat-trick, Matthew Heritage, Dwayne Lewis, and Ryan Smith bagged a brace each and Ben Bergoyne, Danny Marfell, Lewis Meadows and Craig Phillips all netted.
Second-placed side Panteg were held to a 2-2 away draw at Mardy. Goal scorers for Mardy were Simon Wall and Tim Paxton.
Man of the match for Mardy was Matthew Wooles.
Blaenavon Blues battered local rivals Cwmffrwdoer 8-1after James Camage (4), Stephen White (3) and Craig Harris combined to do the damage.
Man of the match for Blaenavon Blues was Stephen White.
There was no change at the top of Division Two after leaders Clydach 'B' won 1-6 away to Pandy 'B'.
Clydach's Ben Ward was in cracking form scoring four of his side's goals. Evan Hall and Luke Welsh scored the rest.
Chris Powell pulled a goal back for Pandy 'B'.
David Morgan was man of the match for Pandy. Ben Ward took man of the match for Clydach 'B'.
Second placed side Prescoed beat Blaenavon Blues 'B' side 2-6. Goalscorers for Prescoed was Lloyd Shirley (3), Gareth Wesson (2) and Barry Jones.
Both of Blaenavon's goals were scored by Josh Bull. Man of the match for Blues was Jack Moore and man of the match for Presoced was Barry Jones.