The "A" in MFA (4)
I believe the answer is:
arts
'the a in mfa' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for arts that I've seen before include "Cultural subjects; skills" , "'Poetry, music, painting (4)'" , "Wiles, skills" , "Aesthetic pursuits for rats" , "Aesthetic pursuits or creations" .)