Work out Kathleen is not going back for a fishy dinner? (8)
I believe the answer is:
plankton
'work out kathleen' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'not going back for a fishy dinner?' is the wordplay.
'going back' shows that the letters should be reversed in order.
'for' says to put letters next to each other (I've seen this in other clues).
'a fishy dinner?' becomes 'plank' (I am not sure about this - if you are sure you should believe this answer much more).
'not' written backwards gives 'ton'.
'ton' put after 'plank' is 'PLANKTON'.
'is' acts as a link.
Can you help me to learn more?
(Other definitions for plankton that I've seen before include "Diminutive drifter" , "Drifting ocean organisms" , "Tiny organisms drifting in the sea" , "Drifters in the sea" , "Whale's staple diet" .)