Call about old students turning (7)
I believe the answer is:
rolling
'turning' is the definition.
(rolling is a kind of turning)
'call about old students' is the wordplay.
'call' becomes 'ring' (telephone call).
'about' is an insertion indicator.
'old' becomes 'o' (abbreviation).
'students' becomes 'LL' (an abbreviation for learner driver written twice).
'o'+'ll'='oll'
'ring' enclosing 'oll' is 'ROLLING'.
(Other definitions for rolling that I've seen before include "Member of musical group ..." , "Type of stock" , "Moving like a wheel" , "Describes a range of rounded hills" , "being so drunk?" .)