Fungus problem around hotel pantry perhaps (8)
I believe the answer is:
mushroom
'fungus' is the definition.
(mushroom is a kind of fungus)
'problem around hotel pantry perhaps' is the wordplay.
'problem' becomes 'sum' (arithmetic problem).
'around' shows that the letters should be reversed in order.
'hotel' becomes 'h' (phonetic alphabet: alpha, bravo, charlie etc.).
'pantry perhaps' becomes 'room' (pantry is a kind of room).
'sum' written backwards gives 'mus'.
'mus'+'h'+'room'='MUSHROOM'
(Other definitions for mushroom that I've seen before include "parasol, for instance" , "expand rapidly" , "Pinkish-brown colour" , "Grow very fast" , "Increase with remarkable rapidity" .)