Faith of one distributing alms (5)
I believe the answer is:
islam
'faith' is the definition.
(I know that Islam is a type of monotheism)
'one distributing alms' is the wordplay.
'one' becomes 'i' (Roman numeral).
'distributing' indicates an anagram.
'alms' is an anagram of 'slam'.
'i'+'slam'='ISLAM'
'of' is the link.
(Other definitions for islam that I've seen before include "Religion based on Muhammad's teachings" , "Adherents of a religion" , "Monotheistic religion" , "Mails to great eastern religion" , "Mails to Muslim religion" .)