Day set, possibly, for a regular date? (6)
I believe the answer is:
steady
'a regular date?' is the definition.
(I've seen this in another clue)
'day set possibly' is the wordplay.
'possibly' indicates an anagram.
'day'+'set'='dayset'
'dayset' anagrammed gives 'STEADY'.
'for' is the link.
(Other definitions for steady that I've seen before include "Firmly supported or balanced" , "Firm; regular" , "Motionless" , "Not liable to fluctuation" , "Maybe 'staid'" .)