Guest finding face covering - it's inside (7)
I believe the answer is:
visitor
'guest' is the definition.
(I've seen this in another clue)
'face covering it's inside' is the wordplay.
'face covering' becomes 'visor'.
'inside' is an insertion indicator.
'visor' enclosing 'it' is 'VISITOR'.
'finding' acts as a link.
(Other definitions for visitor that I've seen before include "One coming to call" , "Company" , "Person turning up" , "Guest - tourist" , "Seasonal migratory bird" .)