Termite (5)
(Other definitions for borer that I've seen before include "Drill" , "Uninteresting type of" , "Hole-making worm or insect" , "Tunnelling worm or insect" , "Insect tunnelling into plant" .)
'termite' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for ant that I've seen before include "A soldier, for one" , "maybe in hill" , "one living in colonies" , "Termite" , "Six-footer" .)