Conviction however is followed by time (7)
I believe the answer is:
thought
'conviction' is the definition.
(conviction can mean a belief)
'however is followed by time' is the wordplay.
'however' becomes 'though' (synonyms).
'is followed by' means one lot of letters go next to another.
'time' becomes 't' (abbreviation).
'though'+'t'='THOUGHT'
(Other definitions for thought that I've seen before include "Idea coming to mind" , "Philosopher must master this" , "Considered, believed" , "Idea, opinion" , "Supposed" .)