Want to follow Branson's first jet? (5)
I believe the answer is:
black
'jet?' is the definition.
(similar in meaning)
'want to follow branson's first' is the wordplay.
'want' becomes 'lack' (synonyms).
'to follow' means one lot of letters go next to another (some letters go after or follow others).
'branson's first' becomes 'b' (1st letter of 'branson').
'lack' put after 'b' is 'BLACK'.
(Other definitions for black that I've seen before include "Very darkest colour" , "Dirty" , "Extremely dark" , "bar" , "-- Monday" .)