Callous, rash and reckless — facing troubles (4,2,5)
I believe the answer is:
hard as nails
'callous' is the definition.
(I've seen this before)
'rash and reckless facing troubles' is the wordplay.
I cannot quite see how this works, but
'and' could be 'n' (common abbreviation for 'and') and 'n' is found within the answer.
'troubles' could be 'ails' (as verb) and 'ails' is found within the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for hard as nails that I've seen before include "without sentiment" , "describing a body builder?" , "tough and > callous?" , "Unyielding and callous" , "Tacky phrase" .)