Risk backing what's in state bank (3)
I believe the answer is:
bet
'risk' is the definition.
(thesaurus)
'backing what's in state bank' is the wordplay.
'backing' is a reversal indicator.
'what's in' indicates the answer is hidden within the clue.
'teb' is hidden in the letters of 'state bank'.
'teb' back-to-front is 'BET'.
(Other definitions for bet that I've seen before include "Wager, back" , "Wager, gamble" , "Speculation" , "Wager, speculate" , "'Stake, wager (3)'" .)