Small group, owing to temperature (4)
I believe the answer is:
duet
'small group' is the definition.
'owing to temperature' is the wordplay.
'owing' becomes 'due' (similar in meaning).
'to temperature' becomes 't' (abbreviation).
'due'+'t'='DUET'
(Other definitions for duet that I've seen before include "Work for two performers" , "A song sung by two" , "Paired performance" , "Work for two players" , "Performance by two" .)