Run from an insect I hear (4)
I believe the answer is:
flee
'run from' is the definition.
(to flee something is to run away from it)
'an insect i hear' is the wordplay.
'an insect' becomes 'flea' (flea is a kind of insect).
'i hear' shows a homophone (sound like).
'flea' is a homophone of 'FLEE'.
(Other definitions for flee that I've seen before include "Run (from danger)" , "rush" , "Turn tail" , "Cut and run" , "Do a runner" .)