Place for sitting president to support American marines (8)
I believe the answer is:
armchair
'place for sitting' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'president to support american marines' is the wordplay.
'president' becomes 'chair' (synonyms).
'to support' is a charade indicator (letters next to each other) (in a down clue, some letters hold others up).
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'marines' becomes 'RM' (abbreviation for 'Royal Marines').
'a'+'rm'='arm'
'chair' after 'arm' is 'ARMCHAIR'.
Can you help me to learn more?
(Other definitions for armchair that I've seen before include "TV viewer's seat" , "Furniture item" , "Seat to relax in" , "Comfy seat" , "Sort of detective" .)