Alpha usurped head honcho in company? (5)

'usurped head honcho in company?' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'alpha' is the wordplay.
I cannot really see how this works, but
'alpha' could be 'a' (phonetic alphabet: alpha, bravo, charlie etc.) and 'a' is found in the answer.
The remaining letters 'tree' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?