Day set out for the firm (6)
I believe the answer is:
steady
'the firm' is the definition.
(I've seen this before)
'day set out' is the wordplay.
'out' indicates an anagram (out can mean wrong or inaccurate).
'day'+'set'='dayset'
'dayset' with letters rearranged gives 'STEADY'.
'for' is the link.
(Other definitions for steady that I've seen before include "Holds course - ...... as she goes" , "Ovisac of some marine creatures" , "Hey" , "Motionless" , "admirer" .)