Playing lute etc in Cos? (7)
I believe the answer is:
lettuce
'cos?' is the definition.
(cos is a kind of lettuce)
'playing lute etc' is the wordplay.
'playing' indicates anagramming the letters.
'lute'+'etc'='luteetc'
'luteetc' anagrammed gives 'LETTUCE'.
'in' acts as a link.
(Other definitions for lettuce that I've seen before include "eg Webbs wonder" , "Plant with broad crisp leaves used in salads" , "Garden plant with edible green leaves, good in salads" , "Salad green" , "Green stuff used in salads" .)