Dropping head of recruitment working for client (6)
I believe the answer is:
patron
'client' is the definition.
(patron is a kind of client)
'dropping head of recruitment working' is the wordplay.
'dropping' becomes 'pat' (eg a cow pat).
'head of' says to take the initial letters.
'working' becomes 'on' (e.g. a machine is working or on).
The initial letter of 'recruitment' is 'r'.
'pat'+'r'+'on'='PATRON'
'for' is the link.
(Other definitions for patron that I've seen before include "Sponsor or supporter as of the arts" , "angel" , "One who protects" , "Financial supporter - customer" , "Sponsor or benefactor" .)