Start returning by tube a lot (5)
I believe the answer is:
debut
'start' is the definition.
(I know that debut is a type of start)
'returning by tube a lot' is the wordplay.
'returning' says the letters should be written backwards.
'by' means one lot of letters go next to another.
'a lot' becomes 'd'.
'tube'+'d' is 'tubed'.
'tubed' reversed gives 'DEBUT'.
(Other definitions for debut that I've seen before include "First appearence as of society girl" , "First attempt" , "opening" , "Appear in public for the first time" , "Beginning, first performance" .)