Hybrid mushroom - no good tucking into that (7)
I believe the answer is:
mongrel
'hybrid mushroom no good tucking into that' is the definition.
'mongrel' can be an answer for 'hybrid' (I've seen this before). I'm not sure about the remainder of the definition.
'hybrid mushroom no good tucking into' is the wordplay.
'hybrid mushroom' becomes 'morel' (morel is a kind of mushroom. I am not sure about the 'hybrid' bit.).
'no good' becomes 'ng' (abbreviation for no and good).
'tucking into' is an insertion indicator.
'morel' going around 'ng' is 'MONGREL'.
Can you help me to learn more?
(Other definitions for mongrel that I've seen before include "of mixed blood" , "Cur" , "of unknown variety" , "bastard" , "Dog of mixed breed" .)