Downsides of taking the lid off Heroes (4)
I believe the answer is:
cons
'downsides' is the definition.
(I've seen this in another clue)
'the lid off heroes' is the wordplay.
'the lid off' means to remove the first letter (in a down clue, lid can mean the top letter).
'heroes' becomes 'icons' (I've seen this in another clue).
'icons' with its initial letter removed is 'CONS'.
'of taking' acts as a link.
(Other definitions for cons that I've seen before include "Swindles" , "Arguments against" , "Tricks" .)