Went to bed, being just about exhausted (7)
I believe the answer is:
retired
'went to bed' is the definition.
('retire' can be a synonym of 'go to bed')
'just about exhausted' is the wordplay.
'just about' becomes 're' ('re' means regarding or about. I am not sure about the 'just' bit.).
'exhausted' becomes 'tired' (exhausted can mean very tired).
're'+'tired'='RETIRED'
'being' acts as a link.
Can you help me to learn more?
(Other definitions for retired that I've seen before include "Withdrew from active participation" , "Gone to bed" , "In bed, withdrew" , "Turned in" , "out of office?" .)