Intellectual sort of lament (6)
I believe the answer is:
mental
'intellectual' is the definition.
(similar in meaning)
'sort of lament' is the wordplay.
'sort of' indicates anagramming the letters.
'lament' with letters rearranged gives 'MENTAL'.
(Other definitions for mental that I've seen before include "like brain operation" , "Lament (anag) - of the mind" , "Cognitive" , "Intellectual" , "Barking" .)