Six-footer, perhaps, in a religious group (6)
I believe the answer is:
insect
'six-footer' is the definition.
(I've seen this before)
'in a religious group' is the wordplay.
'a religious group' becomes 'sect' (eg a religious sect).
'in'+'sect'='INSECT'
'perhaps' acts as a link.
(Other definitions for insect that I've seen before include "Fly, say?" , "Soldier perhaps" , "Praying mantis, say" , "Small invertebrate arthropod" , "Segmented invertebrate" .)