I’m on the phone still (8)
I believe the answer is:
immobile
'still' is the definition.
(I've seen this before)
'i'm on the phone' is the wordplay.
'on' means one lot of letters go next to another.
'the phone' becomes 'mobile' (mobile phone).
'im'+'mobile'='IMMOBILE'
(Other definitions for immobile that I've seen before include "Not moving" , "Motionless" , "stuck in the station, maybe" , "Can't travel" , "Incapable of motion" .)