Silly malarkey making large hot punch (8)
I believe the answer is:
haymaker
'punch' is the definition.
(haymaker is a kind of punch)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for haymaker that I've seen before include "Farm worker - wild punch" , "one working while the sun shines!" , "powerful punch" , "A knockout punch or a grass harvester" , "One profiting from summer weather" .)