Moderate start for combination locks (5)
I believe the answer is:
chair
'moderate' is the definition.
(I know that moderate can be written as chair)
'start for combination locks' is the wordplay.
'start for' says to take the initial letters.
'locks' becomes 'hair' (locks can mean hair).
The initial letter of 'combination' is 'c'.
'c'+'hair'='CHAIR'
(Other definitions for chair that I've seen before include "See 4" , "Head of a university faculty or department" , "A committee's most important seat" , "What professor has" , "Preside over - seat" .)