Sodium - true eccentric - showing character (6)
I believe the answer is:
nature
'character' is the definition.
(I've seen this before)
'sodium true eccentric' is the wordplay.
'sodium' becomes 'NA' (chemical symbol).
'eccentric' indicates an anagram.
'true' anagrammed gives 'ture'.
'na'+'ture'='NATURE'
'showing' acts as a link.
(Other definitions for nature that I've seen before include "Basic character" , "The external, untouched world" , "what's seen in the country?" , "Creation - character" , "Innate quality" .)