Girl hangs onto old recipe for a key material (5)
I believe the answer is:
ivory
'key material' is the definition.
(I've seen this in another clue)
'girl hangs onto old recipe' is the wordplay.
I cannot quite understand how this works, but
'old' could be 'o' (abbreviation) and 'o' is present in the answer.
'recipe' could be 'r' (abbreviation in medical prescriptions) and 'r' is present in the answer.
'girl' could be 'ivy' (woman's name) and 'ivy' is found in the leftover letters.
No letters remain.
This explanation may well be incorrect...
'for a' is the link.
Can you help me to learn more?
(Other definitions for ivory that I've seen before include "National emblem" , "pasty" , "Shade of white" , "Substance of elephant's tusk" , "Key material" .)