Nuts attached to ends of the panel are basic (9)
I believe the answer is:
elemental
'basic' is the definition.
(synonyms)
'nuts attached to ends of the panel are' is the wordplay.
'nuts' becomes 'mental' (I've seen this before).
'attached to' is a charade indicator (letters next to each other).
'ends of' suggests the final letters (I've seen 'end of' mean this).
The last letters of 'the panel are' are 'ele'.
'mental' put after 'ele' is 'ELEMENTAL'.
(Other definitions for elemental that I've seen before include "key" , "Pertaining to weather or to first principles" , "Of basic importance" , "Rising trend" , "of fire, say" .)