Regrettably, a girl can only be heard (4)
I believe the answer is:
alas
'regrettably' is the definition.
('alas' is said before regrettable news)
'a girl can only be heard' is the wordplay.
I cannot quite understand how this works, but
'a' is within the answer.
'girl' could be 'las' (I've seen this in other clues) and 'las' is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
(Other definitions for alas that I've seen before include "I'm sorry to say" , "Exclamation of misfortune" , "Lackaday" , "What a shame!" , "Regretfully!" .)