Bloodless returning spooks keeping nasty (7)
I believe the answer is:
anaemic
'bloodless' is the definition.
(I've seen this before)
'returning spooks keeping nasty' is the wordplay.
'returning' is a reversal indicator.
'spooks' becomes 'CIA' (spooks can mean spies).
'keeping' means one lot of letters goes inside another.
'nasty' becomes 'mean' (similar in meaning).
'cia' enclosing 'mean' is 'cimeana'.
'cimeana' written backwards gives 'ANAEMIC'.
(Other definitions for anaemic that I've seen before include "Pale, lacking vitality" , "Suffering from a lack of red blood cells" , "Pale and weak, lacking vigour" , "Lacking colour or vitality" , "Pale, sickly" .)