Maybe stout guards given revolutionary drug to become more muscular (7)
I believe the answer is:
beefier
'more muscular' is the definition.
(I've seen this in another clue)
'maybe stout guards' is the wordplay.
'maybe' becomes 'fie' (I can't explain this - if you can you should give a lot more credence to this answer).
'stout' becomes 'beer'.
'guards' indicates putting letters inside (inserted letters are guarded).
'fie' placed within 'beer' is 'BEEFIER'.
'given revolutionary drug to become' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Another definition for beefier that I've seen is " Relatively burly".)