The first person seized by robber getting closer (7)
I believe the answer is:
Here is my best explanation:
'closer' is the definition.
Both the answer and definition are comparative adjectives. Maybe there's an association between them I don't understand?
'the first person seized by robber' is the subsidiary indication.
'the first person' becomes 'i'.
'seized by' indicates putting letters inside.
'robber' becomes 'mugger' ('mugger' can be a synonym of 'robber').
'i' going into 'mugger' is 'muggier'.
'getting' is the link.
(Another definition for muggier that I've seen is "closer".)