Give up, at one vacate bed that is being occupied by Tom (8)
I believe the answer is:
abdicate
'give up' is the definition.
(abdicating is a kind of giving up)
'one vacate bed that is being occupied by tom' is the wordplay.
'one' becomes 'a' (a thing is one thing).
'vacate' means to remove the middle letters (I've seen 'vacated' mean this).
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'being occupied by' means one lot of letters goes inside another.
'tom' becomes 'cat' (I have seen 'A tom ' mean 'cat' so perhaps 'tom' could also mean 'cat').
'bed' with its centre taken out is 'bd'.
'ie' enclosing 'cat' is 'icate'.
'a'+'bd'+'icate'='ABDICATE'
'at' acts as a link.
(Other definitions for abdicate that I've seen before include "Give up power" , "surrender" , "Leave throne" , "quit" , "step down" .)