Wild animal said to be nuisance (4)
I believe the answer is:
bore
'be nuisance' is the definition.
(I've seen this before)
'wild animal said' is the wordplay.
'wild animal' becomes 'boar' (I've seen this in another clue).
'said' indicates a 'sounds like' (homophone) clue.
'boar' is a homophone of 'BORE'.
'to' is the link.
(Other definitions for bore that I've seen before include "Hollow out; dull person" , "Tedious thing" , "Push through a crowd" , "Calibre of gun - nuisance" , "Hollow barrel" .)