It sticks close to one spotted? (5)
I believe the answer is:
'it sticks' is the definition.
The definition suggests a singular noun which matches the answer.
'close to one spotted?' is the wordplay.
'close to' indicates one should take the final letters (the close/ending of).
'spotted?' becomes 'poxy' (I can't justify this - if you can you should believe this answer much more).
The last letter of 'one' is 'e'.
Can you help me to learn more?
(Other definitions for epoxy that I've seen before include "Type of adhesive/paint" , "Synthetic adhesive, paint etc." , "Adhesive; plastic" , "Synthetic polymer used in adhesives, paints, etc" , "Type of adhesive" .)