It's bound to come before summer (6)
I believe the answer is:
spring
This clue is a triple definition!
'it's bound' is the first definition.
(both can mean to leap)
'to come' is the second definition.
(thesaurus)
'before summer' is the third definition.
(Other definitions for spring that I've seen before include "Leap, well" , "Start season" , "The vernal season" , "split" , "Wellhead or bounce" .)