Performer in plant ignoring outsiders (5)
I believe the answer is:
actor
'performer' is the definition.
(actor is a kind of performer)
'plant ignoring outsiders' is the wordplay.
'plant' becomes 'factory'.
'ignoring outsiders' says to take the centre.
The centre of 'factory' is 'ACTOR'.
'in' is the link.
(Other definitions for actor that I've seen before include "Thesp" , "Gielgud, say" , "Person performing on stage or screen" , "Films/stage worker" , "Cruise maybe" .)