Inarticulate aides essentially have lower levels of intelligence (4,4)
I believe the answer is:
dumb down
'lower levels of intelligence' is the definition.
(as in lowering the intelligence of something)
'inarticulate aides essentially have' is the wordplay.
'inarticulate' becomes 'dumb' (similar in meaning).
'essentially' means to look at the middle letters.
'have' becomes 'own' (synonyms).
The middle of 'aides' is 'd'.
'dumb'+'d'+'own'='DUMB DOWN'
(Other definitions for dumb down that I've seen before include "Reduce intellectual content of" , "Make less intellectually challenging" , "make things simpler" , "make things easier" , "Make less intellectual" .)