Decay in iron I cut from neat arrangement (9)

'decay' is the definition.

'iron i cut from neat arrangement' is the wordplay.
I cannot really understand how this works, but
'iron' could be 'fe' (Fe is the chemical symbol for iron) and 'fe' is found in the answer.
'i' is within the answer.
'from' could be 'e' (I've seen this in other clues) and 'e' is located in the answer.
This explanation may well be incorrect...

'in' acts as a link.