Treacherous fellow gives drummer cover (7)
I believe the answer is:
reptile
'treacherous fellow' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'drummer cover' is the wordplay.
'drummer' becomes 'rep' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'cover' becomes 'tile' (tiling is a kind of covering).
'rep'+'tile'='REPTILE'
'gives' acts as a link.
Can you help me to learn more?
(Other definitions for reptile that I've seen before include "Malignant creature" , "Cold-blooded vertebrate" , "Cold-blooded beast" , "Turtle, for example" , "Snake or crocodile, say" .)