Sensible article plugging southeast (4)
I believe the answer is:
sane
'sensible' is the definition.
(I've seen this before)
'article plugging southeast' is the wordplay.
'article' becomes 'an' (indefinite article).
'plugging' is an insertion indicator (I've seen this in other clues).
'southeast' becomes 'se' (synonyms).
'an' placed within 'se' is 'SANE'.
(Other definitions for sane that I've seen before include "Sound in mind" , "Healthy in mind" , "Right-minded" , "Rational" , "Compos mentis" .)