Old boy not being seen putting on dress or skirt (4)
I believe the answer is:
ring
'skirt' is the definition.
(both can mean to go around something)
'old boy not being seen putting on dress' is the wordplay.
'old boy' becomes 'OB' (abbreviation for a private school 'old boy').
'not being seen' suggests deleting specific letters.
'putting on dress' becomes 'robing' (getting dressed).
'robing' with 'ob' taken away is 'RING'.
'or' acts as a link.
(Other definitions for ring that I've seen before include "Encircle; arena" , "Circular object - sound" , "Band; arena" , "place for fight" , "Circular band; call" .)