Apathetic Labour's leader in bed (5)
I believe the answer is:
blase
'apathetic' is the definition.
(I've seen this in another clue)
'labour's leader in bed' is the wordplay.
'labour's leader' becomes 'l'.
'in' means one lot of letters goes inside another.
'bed' becomes 'base' (I've seen this in other clues).
'l' placed into 'base' is 'BLASE'.
(Other definitions for blase that I've seen before include "Nonchalantly unconcerned" , "Bored with sable" , "Having a "seen it all before" attitude" , "Surfeited, bored" , "Nonchalant, unconcerned" .)