Heated? Take top off and get ready to fight (5)
I believe the answer is:
armed
'ready to fight' is the definition.
(I've seen this before)
'heated? take top off' is the wordplay.
'heated?' becomes 'warmed' (I've seen this before).
'take top off' means to remove the first letter (I've seen 'taking top off' mean this).
'warmed' with its initial letter taken off is 'ARMED'.
'and get' is the link.
(Other definitions for armed that I've seen before include "Equipped with weapons" , "Provided with weapons" , "With a piece" , "Carrying a weapon" , "Carrying a gun" .)