Having a seat in it, you don't fall (5)
I believe the answer is:
stand
'it you don't fall' is the definition.
The definition suggests a singular noun which matches the answer.
'having a seat' is the wordplay.
I cannot really understand how this works, but
'a' could be 'an' and 'an' is found in the answer.
The remaining letters 'std' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'in' is the link.
Can you help me to learn more?
(Other definitions for stand that I've seen before include "Base < put up with" , "Get to one's feet" , "group of trees" , "Seek election; attitude" , "Tolerate - resistance" .)