Associate cut short offensive husband (6)
I believe the answer is:
attach
'associate' is the definition.
(I've seen this before)
'cut short offensive husband' is the wordplay.
'cut short' means to remove the last letter.
'offensive' becomes 'attack' (an attack is a military offensive).
'husband' becomes 'h'.
'attack' with its last letter removed is 'attac'.
'attac'+'h'='ATTACH'
(Other definitions for attach that I've seen before include "Document carriers" , "Conjoin, tie to" , "Conjoin, affix" , "Annex" , "Stick" .)