Employees find lens prone to break (9)
I believe the answer is:
personnel
'employees' is the definition.
(I've seen this before)
'lens prone to break' is the wordplay.
'to break' is an anagram indicator.
'lens'+'prone'='lensprone'
'lensprone' anagrammed gives 'PERSONNEL'.
'find' acts as a link.
(Other definitions for personnel that I've seen before include "Members of staff" , "Crew" , "Staff complement of an organisation" , "Employees collectively" , "Office" .)