Girl’s bosom lay bare (8)
I believe the answer is:
disclose
'lay bare' is the definition.
(I've seen this before)
'girl's bosom' is the wordplay.
'girl's' becomes 'Dis' (Di is short for Diana).
'bosom' becomes 'close' (similar in meaning).
'dis'+'close'='DISCLOSE'
(Other definitions for disclose that I've seen before include "Uncover" , "Reveal, expose to view" , "Make known - subject is closed" , "broadcast" , "Lay bare" .)