Cabin unknown secretary placed in church showing gall (8)
I believe the answer is:
chutzpah
'gall' is the definition.
(I know that chutzpah is a type of gall)
'cabin unknown secretary placed in church' is the wordplay.
'cabin' becomes 'hut' (both can mean a small building).
'unknown' becomes 'z' (algebra).
'secretary' becomes 'pa' (abbreviation for personal assistant).
'placed in' means one lot of letters goes inside another (I've seen this in other clues).
'church' becomes 'ch' (common abbreviation).
'hut'+'z'+'pa'='hutzpa'
'hutzpa' put into 'ch' is 'CHUTZPAH'.
'showing' is the link.
(Other definitions for chutzpah that I've seen before include "Unbelievable gall; impudence (Yiddish)" , "Cheek or impudence from Hebrew" , "awful cheek" , "Unbelievable audacity (from Yiddish)" , "front" .)