Treatment of teeth: repositioned in head gently, with minimum of effort (6,7)
I believe the answer is:
dental hygiene
'treatment of teeth' is the definition.
(dental treatment)
'repositioned in head gently with minimum of effort' is the wordplay.
'repositioned' indicates anagramming the letters.
'with' means one lot of letters goes inside another.
'minimum of' says to take the initial letters.
The first letter of 'effort' is 'e'.
'in'+'head'+'gently'='inheadgently'
'inheadgently' is an anagram of 'dentalhygine'.
'dentalhygine' going around 'e' is 'DENTAL HYGIENE'.
(Other definitions for dental hygiene that I've seen before include "Prophylactic treatment" , "Cleaning one's teeth etc" .)