Part-time ambassador, having to do housework, failed (3,3,4)
I believe the answer is:
bit the dust
'failed' is the definition.
(to bite the dust is to fail or die)
'part-time ambassador having to do housework' is the wordplay.
'part' becomes 'bit' (both mean a piece of something).
'time' becomes 't' (abbreviation).
'ambassador' becomes 'he' (His or Her Excellency).
'having' means one lot of letters go next to another.
'to do housework' becomes 'dust' (I've seen this in another clue).
'bit'+'t'+'he'+'dust'='BIT THE DUST'
(Another definition for bit the dust that I've seen is " Came to an unfortunate end".)