Spice Girl starts to booze aboard Becks' yacht (4)
I believe the answer is:
baby
'spice girl' is the definition.
(nickname of Emma Bunton in from the Spice Girls)
'starts to booze aboard becks' yacht' is the wordplay.
'starts to' suggests taking the first letters.
The initial letters of 'booze aboard becks yacht' is 'BABY'.
(Other definitions for baby that I've seen before include "needing dummy?" , "Timid person; child" , "Infancy" , "invention" , "Darling" .)