Monster clam in angler's nets, put back (6)
I believe the answer is:
animal
'monster' is the definition.
(thesaurus)
'in angler's nets put back' is the wordplay.
'angler's' becomes 'lama' (I can't justify this - if you can you should give a lot more credence to this answer).
'nets' indicates putting letters inside (some letters are contained or netted).
'put back' shows that the letters should be reversed in order.
'in' put into 'lama' is 'lamina'.
'lamina' written backwards gives 'ANIMAL'.
'clam' acts as a link.
This may not be correct. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for animal that I've seen before include "Living organism characterised by voluntary movement" , "savage" , "Living creature with voluntary motion" , "swine" , "See 26" .)