Gran gets ring back in very short time (10)
I believe the answer is:
nanosecond
'very short time' is the definition.
'gran gets ring back' is the wordplay.
'gran' becomes 'nan' (I've seen this before).
'gets' means one lot of letters go next to another.
'ring' becomes 'o'.
'back' becomes 'second' ('second' can be a synonym of 'back'**).
'nan'+'o'+'second'='NANOSECOND'
'in' is the link.
(Other definitions for nanosecond that I've seen before include "instant?" , "very brief time" , "trice" , "Only a little flash" , "A very short interval of time" .)