Chair: place that one’s occupied (4)
I believe the answer is:
seat
This clue might be a double definition.
'chair' is the first definition.
(something to sit on)
'place that one's occupied' is the second definition.
'seat' can be an answer for 'place' (synonyms). I'm not certain of the rest of the definition.
Can you help me to learn more?
(Other definitions for seat that I've seen before include "Parliamentary constituency" , "MP's place in parliament" , "Chair - bottom" , "'A chair, say (4)'" , "Settle in" .)