Tomfoolery? Not for leaders in Civil Service (6)
I believe the answer is:
antics
'tomfoolery?' is the definition.
(I've seen this before)
'not for leaders in civil service' is the wordplay.
'not for' becomes 'anti' (I've seen this in another clue).
'leaders in' indicates taking the first letters.
The initial letters of 'civil service' is 'cs'.
'anti'+'cs'='ANTICS'
(Other definitions for antics that I've seen before include "Absurd or foolish movements intended to amuse" , "Goings-on, absurd behaviour" , "Tomfoolery" , "Movements intended to be amusing, pranks" , "Amusing behaviour" .)