Watch them maintain article to see it's working (4,2,3,2)
I believe the answer is:
keep an eye on
'watch' is the definition.
(synonyms)
'them maintain article to see it's working' is the wordplay.
I cannot really understand how this works, but
'maintain' could be 'keep' (synonyms) and 'keep' is found within the answer.
'article' could be 'an' (English indefinite article) and 'an' is located in the answer.
'see' could be 'eye' (I've seen this before) and 'eye' is found within the answer.
'working' could be 'on' (on can mean working or activated) and 'on' is found within the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for keep an eye on that I've seen before include "Monitor" , "Watch (someone)" .)