A shade revolutionary, getting stuck into grass? That was the time, perhaps (6)
I believe the answer is:
heyday
'a shade revolutionary getting stuck into grass? that was the time perhaps' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'a shade revolutionary getting stuck into grass?' is the wordplay.
'a shade' becomes 'dye' (I can't explain this - if you can you should give a lot more credence to this answer).
'revolutionary' says the letters should be written in reverse (letters revolve around).
'getting stuck into' means one lot of letters goes inside another.
'grass?' becomes 'hay' (hay is dried grass).
'dye' in reverse letter order is 'eyd'.
'eyd' inserted into 'hay' is 'HEYDAY'.
Can you help me to learn more?
(Other definitions for heyday that I've seen before include "Highest period in someone's career" , "One's peak period" , "Prime of life" , "Period of one's greatest productivity" , "golden age" .)