Be left time to sing loudly (4)
I believe the answer is:
belt
'sing loudly' is the definition.
(synonyms)
'be left time' is the wordplay.
'left' becomes 'l' (common abbreviation).
'time' becomes 't' (abbreviation).
'be'+'l'+'t'='BELT'
'to' acts as a link.
(Other definitions for belt that I've seen before include "boxer's trophy!" , "Heavy blow" , "District" , "Swipe; item of clothing" , "Zone - connecting strip" .)