Occupy with popular practice (7)
I believe the answer is:
inhabit
'occupy' is the definition.
(synonyms)
'with popular practice' is the wordplay.
'with' says to put letters next to each other.
'popular' becomes 'in' ('in' can mean trendy).
'practice' becomes 'habit' (habit is a kind of practice).
'in'+'habit' is 'INHABIT'.
(Other definitions for inhabit that I've seen before include "Live in, occupy" , "Occupy (dwelling)" , "Tenant" , "Occupy - settle" , "people" .)