Call to allow some hair (7)
I believe the answer is:
ringlet
'some hair' is the definition.
(ringlet is a kind of hair)
'call to allow' is the wordplay.
'call' becomes 'ring' (telephone call).
'to allow' becomes 'let' ('let' can be a synonym of 'allow').
'ring'+'let'='RINGLET'
(Other definitions for ringlet that I've seen before include "sort of lock" , "Little curl" , "Handy device" , "Curl of hair; butterfly" , "Hair curl, of an Irish dancer perhaps" .)