Home help's second blunder (5)
I believe the answer is:
gaffe
'blunder' is the definition.
(I know that gaffe is a type of blunder)
'home help's second' is the wordplay.
'home' becomes 'gaff' (I've seen this before).
'help's second' becomes 'e' (2nd letter of 'help').
'gaff'+'e'='GAFFE'
(Other definitions for gaffe that I've seen before include "indiscreet remark" , "Boob" , "Blundering remark" , "Embarrassing blunder" , "Remark one wishes unmade" .)