Loose garment some initially make fun of (5)
I believe the answer is:
smock
'loose garment' is the definition.
(I've seen this before)
'some initially make fun of' is the wordplay.
'initially' suggests taking the first letters.
'make fun of' becomes 'mock' (I've seen this before).
The first letter of 'some' is 's'.
's'+'mock'='SMOCK'
(Other definitions for smock that I've seen before include "Loose dress or blouse" , "Artist's loose overall" , "Artist's, peasant's, overall" , "Loose outer garment" , "artist's attire" .)