An objection to touch (4)
I believe the answer is:
abut
'touch' is the definition.
(abutting is a kind of touching)
'an objection' is the wordplay.
'an' becomes 'a'.
'objection' becomes 'but'.
'a'+'but'='ABUT'
'to' is the link.
(Other definitions for abut that I've seen before include "Adjoin -- 19 (rev)" , "Adjoin, touch" , "Cease (from activity)" , "End or lean against, say a building" , "Adjoin at one end" .)