Age-related loss of self-confidence (3-4,6)
I believe the answer is:
mid-life crisis
'age-related loss of self-confidence' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for mid-life crisis that I've seen before include "Age-related loss of self-confidence" , "Panic often resulting (for men) in ill-advised lifestyle changes" , "An ageing concern?" , "In which someone might lose self-confidence" , "Loss of confidence in one's 40s or 50s, perhaps?" .)