Seat in church at foot of Scottish mountain (5)
I believe the answer is:
bench
'seat' is the definition.
(I know that seat can be written as bench)
'church at foot of scottish mountain' is the wordplay.
'church' becomes 'ch' (common abbreviation).
'at foot of' is a charade indicator (letters next to each other) (in a down clue, some letters go below others).
'scottish mountain' becomes 'ben' (Scottish term for a peak, eg Ben Nevis).
'ch' put after 'ben' is 'BENCH'.
'in' acts as a link.
(Other definitions for bench that I've seen before include "Laboratory work table" , "Long seat for judges" , "Pew or settle" , "Exhibit at dog show" , "Magistrates collectively" .)