In retrospect, young man's fine cutting corners (5)
I believe the answer is:
nooks
'corners' is the definition.
('nook' can be a synonym of 'corner')
'in retrospect young man's fine cutting' is the wordplay.
'in retrospect' says the letters should be written in reverse (in retrospect means looking back).
'young man' becomes 'son' (male child).
'fine' becomes 'OK' (synonyms).
'cutting' means one lot of letters goes inside another (some letters cut their way into a word).
'son' back-to-front is 'nos'.
'nos' enclosing 'ok' is 'NOOKS'.
(Other definitions for nooks that I've seen before include "Niches and crannies" , "out-of-the-way places" , "In security areas" , "Sheltered corners" , "Alcoves" .)