Very small space boy occupies say, in church service (8)
I believe the answer is:
evensong
'church service' is the definition.
(I've seen this before)
'very small space boy occupies say' is the wordplay.
'very' becomes 'v' (abbreviation).
'small space' becomes 'en' (in printing, a space as wide as a letter 'n').
'boy' becomes 'son' (synonyms).
'occupies' is an insertion indicator (inserted letters occupy or enter the word).
'say' becomes 'eg' (both can mean for example).
'v'+'en'+'son'='venson'
'venson' inserted inside 'eg' is 'EVENSONG'.
'in' acts as a link.
(Other definitions for evensong that I've seen before include "Anglican service" , "Church service late in the day" , "Religious service" , "Service of evening prayer in Church of England" , "Late afternoon church service" .)