Procedure popular in a way (7)
I believe the answer is:
routine
'procedure' is the definition.
(I know that procedure can be written as routine)
'popular in a way' is the wordplay.
'popular' becomes 'in' ('in' can mean trendy).
'in' is an insertion indicator.
'a way' becomes 'route' (route is a kind of way).
'in' placed into 'route' is 'ROUTINE'.
(Other definitions for routine that I've seen before include "Fixed sequence of actions" , "Set sequence of actions" , "Regularly performed" , "every day" , "Method" .)