Lois mad about key heroes (5)
I believe the answer is:
idols
'heroes' is the definition.
(I've seen this before)
'lois mad about key' is the wordplay.
'mad' is an anagram indicator.
'about' indicates putting letters inside.
'key' becomes 'd' (musical key).
'lois' with letters rearranged gives 'iols'.
'iols' placed around 'd' is 'IDOLS'.
(Other definitions for idols that I've seen before include "Solid (anag.)" , "False gods" , "Much-admired persons" , "Heroes" , "Graven images sometimes worshipped" .)