Uncomplicated foreign article on PM is backed (6)
I believe the answer is:
Here is my best explanation:
'uncomplicated' is the definition.
('simple' can be a synonym of 'uncomplicated')
'foreign article on pm is backed' is the subsidiary indication.
'foreign article' becomes 'le'.
'on' means one lot of letters go next to another.
'backed' says the letters should be written backwards.
'pmis' reversed gives 'simp'.
'le' put after 'simp' is 'simple'.
(Other definitions for simple that I've seen before include "Not complex, easy to do", "Plain or easy", "Impels (anag.)", "Easy to understand", "Easily done/understood", "Easy; herb", "Impels to be plain", "Straightforward, not elaborate", "Easily understood" and "Easy; plain".)