Someone calling for a mask - that's about it (7)
I believe the answer is:
visitor
'someone' is the definition.
(visitor is a kind of someone)
'a mask that's about it' is the wordplay.
'a mask' becomes 'visor' (I've seen this before).
'that's about' means one lot of letters goes inside another.
'visor' enclosing 'it' is 'VISITOR'.
'calling for' is the link.
(Other definitions for visitor that I've seen before include "Caller, guest" , "who might stay?" , "Company" , "Someone calling (again at 23?)" , "Seasonal migratory bird" .)