Dives from a board, initially cracking head (5)
I believe the answer is:
nabob
'dives from' is the definition.
I can't judge whether this definition defines the answer.
'a board initially cracking head' is the wordplay.
'initially' indicates taking the first letters.
'cracking' means one lot of letters goes inside another (inserted letters go into a gap or crack).
'head' becomes 'nob' (slang term for the head).
The first letter of 'board' is 'b'.
'a'+'b'='ab'
'ab' put within 'nob' is 'NABOB'.
Can you help me to learn more?
(Other definitions for nabob that I've seen before include "Mogul governor; rich man" , "Person of great wealth" , "Nawab" , "moneybags" , "Wealthy influential person" .)