Brave husband goes in quickly (6)
I believe the answer is:
apache
'brave' is the definition.
(I've seen this before)
'husband goes in quickly' is the wordplay.
'husband' becomes 'h' (abbreviation).
'goes in' is an insertion indicator.
'quickly' becomes 'apace' (synonyms).
'h' placed inside 'apace' is 'APACHE'.
(Other definitions for apache that I've seen before include "N American Indian tribe or old Paris ruffian" , "on the streets of Paris" , "Hooligan in Paris" , "Member of a native American people" , "American Indian - French gangster" .)