Setback involving lead and bronze colossus (5)
I believe the answer is:
titan
'colossus' is the definition.
(both can mean something very big)
'setback involving lead and bronze' is the wordplay.
'setback' says the letters should be written backwards.
'involving lead' becomes 'it' (I can't explain this - if you can you should believe this answer much more).
'and' means one lot of letters go next to another.
'bronze' becomes 'tan' (both can mean to get a sun tan).
'it' backwards is 'ti'.
'ti'+'tan'='TITAN'
Can you help me to learn more?
(Other definitions for titan that I've seen before include "Giant of Greek mythology" , "Giant god of Greek myth" , "Largest satellite of Saturn" , "Taint in a legendary giant" , "Huge(ly important) type" .)