A law committed to memory by 1st of October for test (4,4)
I believe the answer is:
oral exam
'test' is the definition.
(I know that oral exam is a type of test)
'a law committed to memory by 1st of october' is the wordplay.
'law' becomes 'lex' (Latin for 'law').
'committed to' indicates putting letters inside (to commit can mean to imprison).
'memory' becomes 'ram' (Random Access Memory on a computer).
'by' says to put letters next to each other.
'ost of october' becomes 'o' (1st letter of 'october').
'a'+'lex'='alex'
'alex' placed inside 'ram' is 'ralexam'.
'ralexam' after 'o' is 'ORAL EXAM'.
'for' is the link.
(Another definition for oral exam that I've seen is " Viva voce test".)