Choose religious group around first half of Lent (6)
I believe the answer is:
select
'choose' is the definition.
(I know that choose can be written as select)
'religious group around first half of lent' is the wordplay.
'religious group' becomes 'sect' (eg a religious sect).
'around' means one lot of letters goes inside another.
'first half of' indicates taking half.
'lent' halved is 'le'.
'sect' enclosing 'le' is 'SELECT'.
(Other definitions for select that I've seen before include "Exclusive - choice" , "best" , "Choice or elite" , "Choice, picked out" , "Choose from several" .)