Make visual contact with a key agent (4)
I believe the answer is:
espy
'make visual contact' is the definition.
'espy' can be an answer for 'make' (thesaurus). I'm not sure about the 'visual contact' bit.
'with a key agent' is the wordplay.
'with' is a charade indicator (letters next to each other).
'a key' becomes 'E' (musical key).
'agent' becomes 'spy' (spy is a kind of agent).
'e'+'spy' is 'ESPY'.
Can you help me to learn more?
(Other definitions for espy that I've seen before include "Observe, notice" , "Catch a glimpse of" , "Watch" , "Make out at a distance" , "Pick out at a distance" .)