Text miser, eccentric zealot (9)
I believe the answer is:
extremist
'zealot' is the definition.
(I've seen this in another clue)
'text miser eccentric' is the wordplay.
'eccentric' indicates anagramming the letters.
'text'+'miser'='textmiser'
'textmiser' anagrammed gives 'EXTREMIST'.
(Other definitions for extremist that I've seen before include "One with highly non-standard views" , "Revolutionary" , "His views are anything but neutral" , "Ultra" , "One far from moderate" .)