For success, it needs a head start (3)
I believe the answer is:
hit
'for success' is the definition.
(hit is a kind of success)
'it needs a head start' is the wordplay.
I cannot really understand how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is found in the answer.
The remaining letters 'hi' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for hit that I've seen before include "Successful song" , "Murder" , "Best-selling record" , "Successful record" , "Strike - great success!" .)