One's closing on criminal finally going straight (6)
I believe the answer is:
'straight' is the definition.
(I've seen this before)
'one's closing on criminal finally going' is the wordplay.
'closing' suggests the final letters (the letter which ends or closes the word).
'on' is an insertion indicator.
'finally' suggests the final letters.
'going' becomes 'inar' (I can't explain this - if you can you should give a lot more credence to this answer).
The final letter of 'one' is 'e'.
The last letter of 'criminal' is 'l'.
'e' inserted into 'linar' is 'LINEAR'.
Can you help me to learn more?
(Other definitions for linear that I've seen before include "Consisting of lines" , "Long and narrow, of one dimension" , "(Of narrative) sequential" , "-- Motor; -- equation" , "Like some ancient scripts" .)