Husband in cloak left union group (6)
I believe the answer is:
chapel
'union group' is the definition.
(I've seen this before)
'husband in cloak left' is the wordplay.
'husband' becomes 'h'.
'in' means one lot of letters goes inside another.
'cloak' becomes 'cape' (cape is a kind of cloak).
'left' becomes 'L' (common abbreviation).
'h' going inside 'cape' is 'chape'.
'chape'+'l'='CHAPEL'
(Other definitions for chapel that I've seen before include "religious building" , "Might he clap in the place of worship?" , "Place of worship set apart in church or cathedral" , "Nonconformist church" , "NUJ members?" .)