Regret limiting attempt, after turning unpredictable (5)
I believe the answer is:
rogue
'unpredictable' is the definition.
(thesaurus)
'regret limiting attempt' is the wordplay.
'regret' becomes 'rue' (to rue something is to regret it).
'limiting' is an insertion indicator.
'attempt' becomes 'og' (I am not sure about this - if you are sure you should believe this answer much more).
'rue' enclosing 'og' is 'ROGUE'.
'after turning' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for rogue that I've seen before include "Stray" , "Old Greek" , "Diseased plant" , "Blackguard" , "Baddie" .)