Sound sheepish like a heavy-hearted bachelor (3)
I believe the answer is:
baa
'sound' is the definition.
(baa is a kind of sound)
'sheepish like a heavy-hearted bachelor' is the wordplay.
I cannot really understand how this works, but
'a' is within the answer.
'bachelor' could be 'ba' (abbreviation for Bachelor of Arts degree) and 'ba' is present in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for baa that I've seen before include "Call from Jacob" , "Sheep's bleat" , "Cry of lamb, sounds angry" , "Lamb's cry" , "to Heathrow, the operators" .)