Quiet, slippery character pinching king’s money (6)
I believe the answer is:
shekel
'money' is the definition.
(currency of Israel)
'quiet slippery character pinching king's' is the wordplay.
'quiet' becomes 'sh' (both can be said to tell someone to be quiet).
'slippery character' becomes 'eel' (slippery fish).
'pinching' means one lot of letters goes inside another (taking inside).
'king' becomes 'K' (abbreviation for king in chess).
'eel' placed around 'k' is 'ekel'.
'sh'+'ekel'='SHEKEL'
(Other definitions for shekel that I've seen before include "One is equal to 100 agorot" , "Israeli currency unit" , "ready in Tel Aviv" , "Israeli coin" , "foreign currency" .)