Cloth fastener covering large contemptible person (7)
I believe the answer is:
reptile
'contemptible person' is the definition.
(reptile can mean a horrible person)
'cloth fastener covering large' is the wordplay.
'cloth' becomes 'rep' (rep is a kind of cloth).
'fastener' becomes 'tie' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'covering' means one lot of letters goes inside another.
'large' becomes 'L' (eg in clothes sizes).
'tie' placed around 'l' is 'tile'.
'rep'+'tile'='REPTILE'
Can you help me to learn more?
(Other definitions for reptile that I've seen before include "Cold-blooded animal like lizard or snake" , "Lizard, for example" , "Somebody grovelling" , "Snake or croc?" , "Eg, snake, lizard, etc" .)