Mineral with yellow colour taken after sickness (5)
I believe the answer is:
fluor
'mineral' is the definition.
(I've seen this before)
'yellow colour taken after sickness' is the wordplay.
'yellow colour' becomes 'or' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'taken after' means one lot of letters go next to another.
'sickness' becomes 'flu' (flu is a kind of sickness).
'or' put after 'flu' is 'FLUOR'.
'with' is the link.
Can you help me to learn more?
(Another definition for fluor that I've seen is " Mineral".)