The last thing to give you warts? (5)
I believe the answer is:
straw
'the last thing' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'give you warts?' is the wordplay.
'warts' can be anagrammed to 'STRAW'.
However, I am not clear how the anagram is indicated.
'to' is the link.
Can you help me to learn more?
(Other definitions for straw that I've seen before include "Thin tube; yellow" , "Thatching material" , "Dried stalks; yellow" , "corny stuff" , "politician" .)