See as the enemy's top agent (4)
I believe the answer is:
espy
'see' is the definition.
(thesaurus)
'the enemy's top agent' is the wordplay.
'top' says to take the initial letters.
'agent' becomes 'spy' (spy is a kind of agent).
The first letter of 'enemys' is 'e'.
'e'+'spy'='ESPY'
'as' is the link.
(Other definitions for espy that I've seen before include "Observe (arch.)" , "Spot at a distance" , "Catch a glimpse of" , "Discern" , "Observe, notice" .)