Weak taste of mushrooms in sauce (4)
I believe the answer is:
limp
'weak' is the definition.
(I've seen this before)
'taste of mushrooms in sauce' is the wordplay.
'taste of mushrooms' becomes 'm' (I can't justify this - if you can you should believe this answer much more).
'in' is an insertion indicator.
'sauce' becomes 'lip' (I've seen this in other clues).
'm' put inside 'lip' is 'LIMP'.
Can you help me to learn more?
(Other definitions for limp that I've seen before include "loose" , "Uneven manner of walking" , "Walk badly; not stiff" , "Flabby - halt" , "obstacle to smooth progress" .)