A cry that has a firm ring to it (3)
I believe the answer is:
coo
'a cry' is the definition.
(coo is a kind of cry)
'a firm ring to it' is the wordplay.
I cannot quite understand how this works, but
'firm' could be 'co' (abbreviation for company) and 'co' is present in the answer.
'ring' could be 'o' (letter resembling a ring) and 'o' is located in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'that has' is the link.
Can you help me to learn more?
(Other definitions for coo that I've seen before include "Murmur, speak softly" , "Sound made by dove" , "Softly say" , "I'm surprised" , "Cry of doves - cry of surprise?" .)