Uselessness following public service (8)
I believe the answer is:
futility
'uselessness' is the definition.
(futility is a kind of uselessness)
'following public service' is the wordplay.
'following' becomes 'f' (used when citing page numbers etc).
'public service' becomes 'utility' (I've seen this before).
'f'+'utility'='FUTILITY'
(Other definitions for futility that I've seen before include "Pointlessness" , "Uselessness" , "No prospect of success" .)