Disheartened aches provide good service (4)
I believe the answer is:
aces
'good service' is the definition.
'aces' can be an answer for 'service' (I have seen 'excellent service' mean 'aces' so perhaps 'service' could also mean 'aces'). I am unsure of the 'good' bit.
'disheartened aches' is the wordplay.
'disheartened' says to hollow out the word (remove centre letters).
'aches' with its middle taken out is 'ACES'.
'provide' is the link.
Can you help me to learn more?
(Other definitions for aces that I've seen before include "Honours" , "Experts (in their field)" , "winning shots" , "winning points" , "wartime pilots?" .)