Support going up and down (9)
I believe the answer is:
bannister
'support going' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe you can see an association between them that I don't see?
'up and down' is the wordplay.
I cannot really understand how this works, but
'up' could be 'is' (I've seen this in other clues) and 'is' is found in the answer.
'and' could be 'n' (common abbreviation for 'and') and 'n' is located in the answer.
The remaining letters 'banter' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
(Other definitions for bannister that I've seen before include "Famous runner" , "safety feature for flight" , "Roger --, four-minute miler" , "Handrail on a staircase" , "Railing on a staircase" .)