Blighter's puppet, is one wearing cap? (9)
I believe the answer is:
toadstool
'one wearing cap?' is the definition.
The definition and answer can be both plants as well as being singular nouns.
Maybe there's an association between them I don't understand?
'blighter's puppet' is the wordplay.
'blighter's' becomes 'toads' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'puppet' becomes 'tool' (synonyms).
'toads'+'tool'='TOADSTOOL'
'is' is the link.
Can you help me to learn more?
(Other definitions for toadstool that I've seen before include "Plant akin to mushroom" , "that could be poisonous" , "what's poisonous maybe" , "Something poisonous" , "Poisonous fungus" .)