Important to be never beaten off (4,4)
I believe the answer is:
nota bene
'important to' is the definition.
I can't tell whether this defines the answer.
'never beaten off' is the wordplay.
'never' becomes 'no' (I've seen this in other clues).
'off' indicates an anagram.
'beaten' anagrammed gives 'tabene'.
'no'+'tabene'='NOTA BENE'
'be' is the link.
Can you help me to learn more?
(Other definitions for nota bene that I've seen before include "'Mark well, in Latin (4,4)'" , "Look carefully" , "Expansion of Latin notation N.B." , "NB in full" , "Observe carefully (Latin)" .)