Trimmed, basic figure idiotic (7)
I believe the answer is:
asinine
'idiotic' is the definition.
(both can mean foolish or silly)
'trimmed basic figure' is the wordplay.
'trimmed' indicates the central letters (the external letters are trimmed from the word).
'figure' becomes 'nine' (I've seen this before).
The centre of 'basic' is 'asi'.
'asi'+'nine'='ASININE'
(Other definitions for asinine that I've seen before include "Jenny's often like this" , "Foolish like donkey" , "Is Annie? (Anag)" , "Senseless" , "Foolish, silly" .)