Highlight small curl of hair (6)
I believe the answer is:
stress
'highlight' is the definition.
(I've seen this before)
'small curl of hair' is the wordplay.
'small curl of' becomes 's' (I am not sure about this - if you are sure you should believe this answer much more).
'hair' becomes 'tress' (tress is a kind of hair).
's'+'tress'='STRESS'
Can you help me to learn more?
(Other definitions for stress that I've seen before include "Particular emphasis" , "Force" , "Underline - tension" , "possible excuse for sickie?" , "Pressure or strain" .)