Sources of minerals brought back from this eroded site (4)
I believe the answer is:
ores
'sources of minerals' is the definition.
'ores' can be an answer for 'minerals' (ore is a kind of mineral). I am unsure of the 'sources of' bit.
'brought back from this eroded site' is the wordplay.
'brought back' shows that the letters should be reversed in order.
'from' says the answer is hidden in the clue.
'sero' is hidden within 'this eroded site'.
'sero' back-to-front is 'ORES'.
Can you help me to learn more?
(Other definitions for ores that I've seen before include "Mined minerals" , "Bauxite, haematite etc" , "Metal-bearing minerals" , "Mineral deposits" , "Sources of metal" .)