Not in favour of a hard worker taking one (4)
I believe the answer is:
anti
'not in favour' is the definition.
(I've seen this before)
'a hard worker taking one' is the wordplay.
'a hard worker' becomes 'ant'.
'taking' says to put letters next to each other.
'one' becomes 'i' (Roman numeral).
'ant'+'i'='ANTI'
'of' acts as a link.
(Other definitions for anti that I've seen before include "Opposition member" , "Prefix meaning against" , "An opponent - opposed to party policy, etc" , "[NO MAN]" , "Who pooh-poohs all" .)