A concern for the old ticker? (10,5)
I believe the answer is:
biological clock
'a concern for' is the definition.
The definition suggests a singular noun which matches the answer.
'old ticker?' is the wordplay.
I cannot really understand how this works, but
'old' could be 'o' (common abbreviation eg in OE for Old English) and 'o' is located in the answer.
'ticker?' could be 'clock' (I've seen this in another clue) and 'clock' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'the' is the link.
Can you help me to learn more?
(Other definitions for biological clock that I've seen before include "Innate mechanism" , "Vital timer" .)