Native American quickly concealing husband (6)
I believe the answer is:
apache
'native american' is the definition.
(group of Native American tribes)
'quickly concealing husband' is the wordplay.
'quickly' becomes 'apace' (synonyms).
'concealing' is an insertion indicator.
'husband' becomes 'h' (abbreviation).
'apace' enclosing 'h' is 'APACHE'.
(Other definitions for apache that I've seen before include "American Indian once found in Paris" , "Parisian ruffian - Indian" , "settler in Oklahoma?" , "American Indian - French gangster" , "North American native tribe" .)