New vaper, fast becoming widespread (9)
I believe the answer is:
prevalent
'widespread' is the definition.
(I've seen this before)
'new vaper fast' is the wordplay.
'new' is an anagram indicator.
'fast' becomes 'lent' (Lent is a period of fasting in Christianity).
'vaper' is an anagram of 'preva'.
'preva'+'lent'='PREVALENT'
'becoming' is the link.
(Other definitions for prevalent that I've seen before include "powerful" , "general" , "Commonplace" , "Ruling" , "Widespread - current" .)