Phosphorus or potassium found in meat (4)
I believe the answer is:
pork
'meat' is the definition.
(I know that pork is a type of meat)
'phosphorus or potassium' is the wordplay.
'phosphorus' becomes 'P' (P is the chemical symbol for phosphorus).
'potassium' becomes 'K' (K is the chemical symbol for potassium).
'p'+'or'+'k'='PORK'
'found in' is the link.
(Other definitions for pork that I've seen before include "Pig flesh" , "Meat used in sausages" , "Bacon, e.g." , "Pig's flesh as food" , "Pigmeat" .)