Supporting one's bottom (6)
I believe the answer is:
behind
This might be a double definition.
'supporting one's' is the first definition.
'behind' can be an answer for 'supporting' (I've seen this in another clue). I'm not certain of the 'one's' bit.
'bottom' is the second definition.
(synonyms)
Can you help me to learn more?
(Other definitions for behind that I've seen before include "Seat" , "bum" , "in van? No" , "Responsible for" , "Hidden by; bottom" .)