Seat on which one may have sat for lb50 (5)
I believe the answer is:
stall
'seat on which one' is the definition.
'stall' can be an answer for 'seat' (I've seen this before). I am not sure about the remainder of the definition.
'sat for lb50' is the wordplay.
I cannot really understand how this works, but
an anagram of 'sat' is 'sta' which is located in the answer.
This may be the basis of the clue (or it may be nonsense).
'may have' is the link.
Can you help me to learn more?
(Other definitions for stall that I've seen before include "Booth; prevaricate" , "Be evasive" , "Kiosk" , "Cowshed or stable" , "seat in church" .)