I am on phone, still (8)
I believe the answer is:
immobile
'still' is the definition.
(I've seen this before)
'i am on phone' is the wordplay.
'i am' becomes 'I'm' (contraction).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'phone' becomes 'mobile phone' (mobile phone).
'im'+'mobile'='IMMOBILE'
(Other definitions for immobile that I've seen before include "Motionless" , "Not capable of movement" , "Incapable of motion" , "Static" , "Can't travel" .)