Radical currently turning up in factory is to do marvellous stuff (4,7)

'to do marvellous stuff' is the definition.
(to work wonders is to perform miracles or marvels)

'radical currently turning up in factory' is the wordplay.
'radical' becomes 'red' (I've seen this in other clues).
'currently' becomes 'now' (I've seen this in other clues).
'turning up' says the letters should be written backwards.
'in' is an insertion indicator.
'factory' becomes 'works' (I've seen this before).
'red'+'now'='rednow'
'rednow' written backwards gives 'wonder'.
'wonder' going within 'works' is 'WORK WONDERS'.

'is' acts as a link.