Society nowadays is gloomy (3)
I believe the answer is:
sad
'gloomy' is the definition.
(similar in meaning)
'society nowadays' is the wordplay.
'society' becomes 's' (common abbreviation in names of organisations).
'nowadays' becomes 'AD' (AD, Anno Domini, as opposed to BC, Before Christ).
's'+'ad'='SAD'
'is' is the link.
(Other definitions for sad that I've seen before include "Doleful" , "Deplorable" , "Dejected" , "grey" , "Tragic" .)