An excuse to leap wildly? (4)
I believe the answer is:
plea
'an excuse' is the definition.
(thesaurus)
'leap wildly?' is the wordplay.
'wildly?' indicates an anagram (I've seen 'wildly' mean this).
'leap' with letters rearranged gives 'PLEA'.
'to' is the link.
(Other definitions for plea that I've seen before include "Excuse, entreaty" , "Intercession" , "Formal statement of guilty or not guilty" , "suit" , "Excuse - pretext" .)