Family blunders? Not half (4)
I believe the answer is:
clan
'family' is the definition.
(thesaurus)
'blunders? not half' is the wordplay.
'blunders?' becomes 'clangers' (clanger is a kind of blunder).
'not half' suggests halving the letters.
'clangers' halved is 'CLAN'.
(Other definitions for clan that I've seen before include "Tribal family" , "Scots family group" , "Extended family as in Scotland" , "Kinship group" , "Campbells, say?" .)