Gunk from small piece of fruit (5)
I believe the answer is:
slime
'gunk' is the definition.
(I know that gunk can be written as slime)
'small piece of fruit' is the wordplay.
'small' becomes 'slim' (similar in meaning).
'piece of fruit' becomes 'e' (I can't explain this - if you can you should believe this answer much more).
'slim'+'e'='SLIME'
'from' acts as a link.
Can you help me to learn more?
(Other definitions for slime that I've seen before include "Goo" , "Gooey seeping stuff" , "Nasty slippery stuff" , "Slippery mud; slug trail" , "Gunge" .)