Gathers outside in elements supporting a religious service (7)
I believe the answer is:
amasses
'gathers' is the definition.
('amass' can be a synonym of 'gather')
'outside in elements supporting a religious service' is the wordplay.
'outside in' says to hollow out the word (remove centre letters) (only the letters on the outside).
'supporting' says to put letters next to each other (in a down clue, some letters go below others).
'religious service' becomes 'mass' (mass in a church).
'elements' with its middle removed is 'es'.
'a'+'mass'='amass'
'es' put after 'amass' is 'AMASSES'.
(Other definitions for amasses that I've seen before include "'Accumulates, gathers (7)'" , "Gathers together" , "Collects" .)