He can either phone or come round in person (6)
I believe the answer is:
caller
'person' is the definition.
(caller is a kind of person)
'he can either phone or come round' is the wordplay.
I cannot really understand how this works, but
'he' could be 'cal' and 'cal' is located in the answer.
This explanation may well be incorrect...
'in' acts as a link.
Can you help me to learn more?
(Other definitions for caller that I've seen before include "Visitor" , "Someone phoning" , "Person on the line" , "One visits" , "One paying a brief visit" .)