Tangerine's skin in sloppy plant secretion (5)
I believe the answer is:
latex
'plant secretion' is the definition.
(milky fluid from plants)
'tangerine's skin in sloppy' is the wordplay.
'skin' says to hollow out the word (remove centre letters).
'in' indicates putting letters inside.
'sloppy' becomes 'lax' (I've seen this before).
'tangerine' with its centre removed is 'te'.
'te' going within 'lax' is 'LATEX'.
(Other definitions for latex that I've seen before include "Plant material, used to make rubber" , "Liquid used in making rubber" , "Stretchy stuff" , "Milky substance produced by some trees" , "Synthetic product" .)