Select new top (3)
I believe the answer is:
opt
'select' is the definition.
(I've seen this in another clue)
'new top' is the wordplay.
'new' is an anagram indicator.
'top' anagrammed gives 'OPT'.
(Other definitions for opt that I've seen before include "Prefer, choose" , "Decide between possibilities, choose" , "Make a choice" , "Elect" , "Select as a preferable alternative" .)