For a bighead, the ultimate blow (5)
I believe the answer is:
blast
'blow' is the definition.
(I know that blow can be written as blast)
'for a bighead the ultimate' is the wordplay.
I cannot really understand how this works, but
'a' is within the answer.
'bighead' could be 'b' (the head letter of 'big') and 'b' is found in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for blast that I've seen before include "Report" , "Severely criticise" , "Effect of explosion" , "Great time: explosion" , "Loud horn sound" .)