At bottom, a source of support (4)
I believe the answer is:
seat
I believe this is a triple definition!
'at bottom' is the first definition.
'seat' can be an answer for 'bottom' (synonyms). I am unsure of the 'at' bit.
'a source' is the second definition.
(I've seen this in another clue)
'of' acts as a link.
'support' is the third definition.
(I know that seat is a type of support)
Can you help me to learn more?
(Other definitions for seat that I've seen before include "pew?" , "Chair - bottom" , "Settle in" , "Place to sit" , "Position (in parliament)" .)