Instant mousse conditioner bottles (6)
I believe the answer is:
second
'instant' is the definition.
(I know that instant can be written as second)
'mousse conditioner bottles' is the wordplay.
'bottles' says the answer is hidden in the clue (bottling is a kind of containing).
'SECOND' is hidden within 'mousse conditioner'.
(Other definitions for second that I've seen before include "Support - runner-up" , "Time for a supporter" , "bit" , "Subordinate; moment" , "tick" .)