Reserve medicines — spare bottles (7)
I believe the answer is:
iciness
'reserve' is the definition.
(I've seen this in another clue)
'medicines spare bottles' is the wordplay.
'bottles' says the answer is hidden in the clue (bottling is a kind of containing).
'ICINESS' is hidden in the letters of 'medicines spare'.
(Other definitions for iciness that I've seen before include "Frozen state of" , "Chill; reserve" , "Hostile attitude" , "Extreme chill" , "Frostiness" .)