Tension from opening of secure lock (6)
I believe the answer is:
stress
'tension' is the definition.
(I know that tension can be written as stress)
'opening of secure lock' is the wordplay.
'opening of' suggests taking the first letters.
'lock' becomes 'tress' (both can mean a piece of hair).
The first letter of 'secure' is 's'.
's'+'tress'='STRESS'
'from' is the link.
(Other definitions for stress that I've seen before include "result of being overworked" , "what causes tension" , "nervous tension" , "suffering" , "possible excuse for sickie?" .)