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 wordplay.
'foreign article' becomes 'le'.
'on' is a charade indicator (letters next to each other).
'backed' says the letters should be written backwards.
'pmis' back-to-front is 'simp'.
'le' put after 'simp' is 'SIMPLE'.
(Other definitions for simple that I've seen before include "Plant with medicinal properties", "The sort of interest", "Naive", "half-witted", "Easy; plain", "Straightforward, not elaborate", "Easy; herb", "Not complex, complicated or involved", "Uncomplicated; herb" and "Plain or easy".)