Reserves support look good (7)
I believe the answer is:
backlog
'reserves' is the definition.
(thesaurus)
'support look good' is the wordplay.
'support' becomes 'back' (back is a kind of support).
'look' becomes 'lo'.
'good' becomes 'g' (abbreviation).
'back'+'lo'+'g'='BACKLOG'
(Other definitions for backlog that I've seen before include "work piling up" , "An arrear as of work" , "Build-up of work still to be dealt with" , "Accumulation of uncompleted work" , "Work piled up" .)