Starts to leap around, yell and thrash (4,3)
I believe the answer is:
lash out
'thrash' is the definition.
Both the definition and answer are verbs in their base form.
Perhaps you can see a link between them that I can't see?
'starts to leap around yell' is the wordplay.
'starts to' says to take the initial letters.
'yell' becomes 'shout' (synonyms).
The initial letters of 'leap around' is 'la'.
'la'+'shout'='LASH OUT'
'and' is the link.
Can you help me to learn more?
(Other definitions for lash out that I've seen before include "Attack, verbally or physically" , "unprovoked attack" , "Spend lots" , "Wildly attack" , "Spend extravagantly" .)