Blunder boss detailed (5)
I believe the answer is:
gaffe
'blunder' is the definition.
(gaffe is a kind of blunder)
'boss detailed' is the wordplay.
'boss' becomes 'gaffer' ('gaffer' can be a synonym of 'boss').
'detailed' means to remove the last letter (the word must be end-less or 'de-tailed').
'gaffer' with its final letter taken away is 'GAFFE'.
(Other definitions for gaffe that I've seen before include "A blunder, faux pas" , "Social blunder" , "indiscreet remark" , "Indiscretion" , "Boob" .)