Deserve 1000 coming back weary? (5)
I believe the answer is:
merit
'deserve' is the definition.
('merit' can be a synonym of 'deserve')
'1000 coming back weary?' is the wordplay.
'1000' becomes 'm' ('m' can be a synonym of '1000').
'coming back' says the letters should be written in reverse.
'weary?' becomes 'tire' ('tire' can be a synonym of 'weary').
'tire' reversed gives 'erit'.
'm'+'erit'='MERIT'
(Other definitions for merit that I've seen before include "Deserve, be worthy of" , "Excellence that deserves to be honoured" , "Advantage" , "credit" , "Goodness" .)