Candidate left in charge, following a very quiet worker (9)
I believe the answer is:
applicant
'candidate' is the definition.
(I've seen this before)
'left in charge following a very quiet worker' is the wordplay.
'left' becomes 'l' (common abbreviation).
'in charge' becomes 'ic' (abbreviation for 'in charge').
'following' is a charade indicator (letters next to each other).
'very quiet' becomes 'pp' (musical abbreviation for pianissimo).
'worker' becomes 'ant' (worker is a type of ant).
'l'+'ic'='lic'
'a'+'pp'='app'
'lic' put after 'app' is 'applic'.
'applic'+'ant'='APPLICANT'
(Other definitions for applicant that I've seen before include "one looking for a job" , "Candidate for job" , "someone wanting a job" , "Candidate for a post" , "Job seeker" .)