A young girl’s in hearing, I'm sorry to say (4)
I believe the answer is:
alas
'i'm sorry to say' is the definition.
(I've seen this before)
'a young girl's in hearing' is the wordplay.
'young girl's' becomes 'lass'' ('lass' can be a synonym of 'young girl').
'in hearing' indicates a 'sounds like' (homophone) clue.
'lass' sounds like 'las'.
'a'+'las'='ALAS'
(Other definitions for alas that I've seen before include "'- Poor Yorick' (Hamlet)" , "I'm sorry to say" , "Too bad, so sad" , "Regretfully!" , "Unhappily" .)