Run from active agent (3)
I believe the answer is:
spy
'agent' is the definition.
(spy is a kind of agent)
'run from active' is the wordplay.
'run' becomes 'r' (cricket abbreviation).
'from' indicates named letters should be taken away.
'active' becomes 'spry' ('spry' can be similar in meaning to 'active').
'spry' with 'r' removed is 'SPY'.
(Other definitions for spy that I've seen before include "Undercover agent" , "Mole, agent" , "One gathers information surreptitiously" , "Enemy agent" , "One who collects secret information as for government" .)