Slow-witted Hobbits regularly ignored exercise (6)
I believe the answer is:
obtuse
'slow-witted' is the definition.
(I've seen this before)
'hobbits regularly ignored exercise' is the wordplay.
'regularly ignored' indicates alternate letters.
'exercise' becomes 'use' (synonyms).
The alternating letters of 'hobbits' are 'obt'.
'obt'+'use'='OBTUSE'
(Other definitions for obtuse that I've seen before include "Dense, dim about the angle" , "Angle greater than 90 degrees" , "Dull, non-perceptive" , "A stupid angle?" , "boneheaded?" .)