First of letters penned by women concerning seducer (4)
I believe the answer is:
Here is my best explanation:
'seducer' is the definition.
(I've seen this before)
'first of letters penned by women concerning' is the wordplay.
'first of' suggests taking the first letters.
'penned by' is an insertion indicator.
'women' becomes 'w'.
'concerning' becomes 'of'.
The initial letter of 'letters' is 'l'.
'l' placed within 'wof' is 'WOLF'.
(Other definitions for wolf that I've seen before include "Dog-like animal - womaniser", "Seducer - gobble down", "Pack-hunting carnivore", "Pack hunter", "Predatory canine animal", "philanderer", "Austrian composer", "Lothario", "Beast, member of pack" and "Pack-hunting animal".)