Genuine regret shown after time (4)
I believe the answer is:
true
'genuine' is the definition.
(I know that genuine can be written as true)
'regret shown after time' is the wordplay.
I cannot quite understand how this works, but
'regret' could be 'rue' (to rue something is to regret it) and 'rue' is found in the answer.
'time' could be 't' (abbreviation) and 't' is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for true that I've seen before include "Agreeing with fact or reality" , "Unwavering" , "Real; accurate" , "Loyal; authentic" , "Real, actual" .)