Unusually poised as saint, showing no emotion (13)
I believe the answer is:
dispassionate
'showing no emotion' is the definition.
'unusually poised as saint' is the wordplay.
'unusually' indicates anagramming the letters.
'poised'+'as'+'saint'='poisedassaint'
'poisedassaint' is an anagram of 'DISPASSIONATE'.
(Other definitions for dispassionate that I've seen before include "Rational, impartial" , "Imperturbable" , "taking the unbiased view?" , "Not affected by personal feelings" , "Objective, unemotional" .)