Most ardent laments in Shakespeare's time? (7)
I believe the answer is:
keenest
'most ardent' is the definition.
Both the answer and definition are superlative adjectives. Maybe there's an association between them I don't understand?
'laments in shakespeare's time?' is the wordplay.
'laments in shakespeare' becomes 'keen' (I am not sure about this - if you are sure you should believe this answer much more).
'time?' becomes 'est' (EST is an example).
'keen'+'est'='KEENEST'
(Other definitions for keenest that I've seen before include "Sharpest" , "Most interested or sharp" , "most sensitive" , "Most anxious" , "most piercing" .)