Act to probe the iron spread out in mineral (9)

'mineral' is the definition.
(thesaurus)

'act to probe the iron spread out' is the wordplay.
I cannot quite understand how this works, but
'act' could be 'do' (to do is to act or execute a task) and 'do' is located in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is present in the answer.
This may be the basis of clue (or it may be nonsense).

'in' acts as a link.