A blockhead to the very end, dammit! (5)
I believe the answer is:
blast
'dammit' is the definition.
(both are mild expletives)
'a blockhead to the very end' is the wordplay.
'a blockhead' becomes 'b' (head letter of 'block').
'to' says to put letters next to each other.
'the very end' becomes 'last' (I've seen this before. I am not sure about the 'very' bit.).
'b'+'last'='BLAST'
Can you help me to learn more?
(Other definitions for blast that I've seen before include "Explosion - mild oath" , "Loud noise from a horn" , "Severe reprimand; strong gust" , "Blow up or swear" , "Report" .)