Bolt gathered to secure new clock mechanism (10)
I believe the answer is:
escapement
'clock mechanism' is the definition.
(I've seen this before)
'bolt gathered to secure new' is the wordplay.
'bolt' becomes 'escape' (I've seen this before**).
'gathered' becomes 'met' ('meet' can be a synonym of 'gather').
'to secure' indicates putting letters inside.
'new' becomes 'n'.
'met' enclosing 'n' is 'ment'.
'escape'+'ment'='ESCAPEMENT'
(Other definitions for escapement that I've seen before include "Part of A Clockwork" , "Part of watch mechanism" , "Clock or watch mechanism" , "One-time flight" , "piano piece" .)