Basic telex with edges missing occupying the mind (9)
I believe the answer is:
elemental
'basic' is the definition.
(synonyms)
'telex with edges missing occupying the mind' is the wordplay.
'with edges missing' means to look at the middle letters (letters at the edge removed).
'occupying the mind' becomes 'mental' (using mental faculties).
The central letters of 'telex' are 'ele'.
'ele'+'mental'='ELEMENTAL'
(Other definitions for elemental that I've seen before include "Let me lean like forces of nature" , "Of basic importance" , "Essential" , "Basic, rudimentary" , "Of nature's powers" .)