Objection over temperature target (4)
I believe the answer is:
butt
'target' is the definition.
('butt' can be a synonym of 'target')
'objection over temperature' is the wordplay.
'objection' becomes 'but'.
'over' is a charade indicator (letters next to each other).
'temperature' becomes 't' (abbreviation).
'but'+'t'='BUTT'
(Other definitions for butt that I've seen before include ""bottom" to US" , "Object of scorn, of humour" , "Knock head" , "at 16 down [MAN UNITED]" , "Attack" .)