Plug nowadays - it's ever-changing (9)
I believe the answer is:
advertise
'plug' is the definition.
(I've seen this before)
'nowadays it's ever-changing' is the wordplay.
'nowadays' becomes 'AD' (AD, Anno Domini, as opposed to BC, Before Christ).
'changing' is an anagram indicator.
'its'+'ever'='itsever'
'itsever' with letters rearranged gives 'vertise'.
'ad'+'vertise'='ADVERTISE'
(Other definitions for advertise that I've seen before include "Call public attention to" , "Make public what is for sale" , "Publicize, call attention to" , "Publicise, promote" , "Publicise, call attention to" .)