Bum absolutely exhausted, no space (8)
I believe the answer is:
deadbeat
'bum' is the definition.
(I've seen this before)
'absolutely exhausted no space' is the wordplay.
'absolutely' becomes 'dead' (synonyms).
'exhausted no space' becomes 'beat' (I can't justify this - if you can you should give a lot more credence to this answer).
'dead'+'beat'='DEADBEAT'
Can you help me to learn more?
(Other definitions for deadbeat that I've seen before include "idle so-and-so" , "idler" , "lazy so-and-so" , "extremely tired" , "Vagrant's" .)