Creature kept scratching head in anger (7)
I believe the answer is:
reptile
'creature' is the definition.
(I have seen 'Malignant creature' mean 'reptile' so perhaps 'creature' could also mean 'reptile')
'kept scratching head in anger' is the wordplay.
'scratching head' means to remove the first letter.
'in' means one lot of letters goes inside another.
'anger' becomes 'rile' (I've seen this in other clues).
'kept' with its initial letter taken away is 'ept'.
'ept' inserted into 'rile' is 'REPTILE'.
(Other definitions for reptile that I've seen before include "Lizard, for example" , "Cold-blooded beast" , "Cold-blooded creature" , "Serpent" , "Unpleasant character" .)