People into steel alloy components (8)
I believe the answer is:
elements
'components' is the definition.
('element' can be a synonym of 'component')
'people into steel alloy' is the wordplay.
'people' becomes 'men' (men can refer to humanity as a whole).
'into' means one lot of letters goes inside another.
'alloy' indicates anagramming the letters.
'steel' is an anagram of 'elets'.
'men' inserted inside 'elets' is 'ELEMENTS'.
(Other definitions for elements that I've seen before include "Parts of something or the weather" , "Components, factors" , "Constituents, ingredients" , "He and I are two" , "Components or weather conditions" .)