Incumbent at first on females, one not so friendly, to relay pardon (12)
I believe the answer is:
officeholder
'incumbent' is the definition.
(synonyms)
'first on females one not so friendly to relay pardon' is the wordplay.
I cannot really understand how this works, but
'first' could be 'i' (I in Roman numerals eg Elizabeth I) and 'i' is found within the answer.
'on' could be 'o' (I've seen this in other clues) and 'o' is located in the answer.
'females' could be 'ff' (the abbreviation for female repeated) and 'ff' is found within the answer.
'one' could be 'er' (I've seen this in other clues) and 'er' is found in the answer.
'not' could be 'o' (I've seen this in other clues) and 'o' is found within the answer.
This may be the basis of clue (or it may be nonsense).
'at' acts as a link.