Control of the one in inner turmoil (4,2)
I believe the answer is:
rein in
'control' is the definition.
(I know that control is a is a more specific form of the action of rein in)
'one in inner turmoil' is the wordplay.
'one' becomes 'i' (Roman numeral).
'in' is an insertion indicator.
'turmoil' indicates anagramming the letters (I've seen this in other clues).
'inner' with letters rearranged gives 'renin'.
'i' inserted within 'renin' is 'REIN IN'.
'of the' is the link.
(Other definitions for rein in that I've seen before include "Person of great power" , "Control" , "Restrain (someone)" .)