Always in prayer (3)
I believe the answer is:
aye
'always' is the definition.
(archaic term for 'always')
'in prayer' is the wordplay.
'in' says the answer is hidden in the clue.
'AYE' is hidden within 'prayer'.
(Other definitions for aye that I've seen before include "Word of assent" , "One voting in favour" , "Entirely one" , "Yes answer in voting" , "Always" .)