One with faith in artist putting time into expedition (9)

'one with faith' is the definition.
(member of the Rastafarian faith)

'artist putting time into expedition' is the wordplay.
I cannot quite see how this works, but
'artist' could be 'ra' (Royal Academician, member of Royal Academy of Arts) and 'ra' is found within the answer.
'time' could be 't' (abbreviation) and 't' is present in the answer.
'expedition' could be 'safari' (safari is a kind of expedition) and 'safari' is found within the remaining letters.
This accounts for all the letters.
This explanation may well be incorrect...

'in' acts as a link.