Requests by master to abandon disguises (4)
I believe the answer is:
asks
'requests' is the definition.
('ask' can be a synonym of 'request')
'master to abandon disguises' is the wordplay.
'master' becomes 'M' (common abbreviation eg MA, Master of Art).
'to abandon' suggests deleting specific letters.
'disguises' becomes 'masks' (masking is a kind of disguising).
'masks' with 'm' taken out is 'ASKS'.
'by' is the link.
(Other definitions for asks that I've seen before include "Invites; enquires" , "is curious" , "Makes an inquiry" , "Inquiries" , "Puts a query" .)