Inhibit (5)
'inhibit' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for deter that I've seen before include "Discourage (someone from an action)" , "Frighten off; prevent" , "Warn off" , "Inhibit" , "Try to prevent" .)
(Other definitions for cramp that I've seen before include "Muscle spasm" , "Muscular spasm, very painful" , "Confine - muscular spasm" , "Painful muscular contraction" , "Sudden painful tightening of a muscle" .)