Accumulate a service (5)
I believe the answer is:
amass
'accumulate' is the definition.
(synonyms)
'a service' is the wordplay.
'service' becomes 'mass' (I've seen this in other clues).
'a'+'mass'='AMASS'
(Other definitions for amass that I've seen before include "Accumulate, pile up" , "Sodium chloride" , "Be a compiler" , "store" , "run up?" .)