Nowadays to correspond is sufficient (8)
I believe the answer is:
adequate
'sufficient' is the definition.
(similar in meaning)
'nowadays to correspond' is the wordplay.
'nowadays' becomes 'AD' (AD, Anno Domini, as opposed to BC, Before Christ).
'to correspond' becomes 'equate' ('equate' can be a synonym of 'correspond').
'ad'+'equate'='ADEQUATE'
'is' acts as a link.
(Other definitions for adequate that I've seen before include "'Satisfactory, acceptable (8)'" , "plenty" , "Enough to meet a purpose" , "Just about sufficient, acceptable" , "up to the job?" .)