Not exactly a man to excite, with energy going spare (10)
I believe the answer is:
cadaverous
'spare' is the definition.
(thesaurus)
'not exactly a man to excite with' is the wordplay.
'not exactly' becomes 'ca' (circa).
'a man' becomes 'dave' (I've seen this before).
'to excite with' becomes 'rous' (I can't justify this - if you can you should believe this answer much more).
'ca'+'dave'+'rous'='CADAVEROUS'
'energy going' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for cadaverous that I've seen before include "Skeletal" , "not looking healthy" , "Corpse-like" , "Gaunt" , "Unhealthy-looking" .)