Teutonic god snatching old lady's mantle, showing no emotion (8)
I believe the answer is:
woodenly
'showing no emotion' is the definition.
'teutonic god snatching old lady's mantle' is the wordplay.
'teutonic god' becomes 'woden'.
'snatching' means one lot of letters goes inside another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'mantle' suggests removing the centre (mantle can mean the cover or outside of something).
'lady' with its middle removed is 'ly'.
'woden' going around 'o' is 'wooden'.
'wooden'+'ly'='WOODENLY'
(Another definition for woodenly that I've seen is " Stiffly, awkwardly".)