Hood put on girl's head when dressing? (6)
I believe the answer is:
robing
'dressing?' is the definition.
(robing is a kind of dressing)
'hood put on girl's head' is the wordplay.
'hood' becomes 'robin' (I've seen this in another clue).
'put on' is a charade indicator (letters next to each other).
'head' says to take the initial letters.
The first letter of 'girls' is 'g'.
'robin'+'g'='ROBING'
'when' is the link.
(Other definitions for robing that I've seen before include "dressing up" , "clothing" .)