It takes time to become such a thief (15)
I believe the answer is:
procrastination
'thief' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'it takes time to become such a' is the wordplay.
I cannot quite understand how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is found in the answer.
'time' could be 't' (abbreviation) and 't' is present in the answer.
'a' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for procrastination that I've seen before include "Delaying or postponement of action" , "Delaying behaviour" , "Dilly-dallying" , "Deferral" , "Time-wasting" .)