Sufficient nowadays to regard as equal (8)
I believe the answer is:
adequate
'sufficient' is the definition.
(similar in meaning)
'nowadays to regard as equal' is the wordplay.
'nowadays' becomes 'AD' (AD, Anno Domini, as opposed to BC, Before Christ).
'to regard as equal' becomes 'equate' (to equate two things is to regard them as equal).
'ad'+'equate'='ADEQUATE'
(Other definitions for adequate that I've seen before include "Sufficient, good enough" , "plenty" , "Ample" , "'Satisfactory, acceptable (8)'" , "up to the job?" .)