Ooze across back of barrel and drop off (5)
I believe the answer is:
sleep
'drop off' is the definition.
(thesaurus)
'ooze across back of barrel' is the wordplay.
'ooze' becomes 'seep' ('seep' can be a synonym of 'ooze'**).
'across' is an insertion indicator.
'back of' indicates one should take the final letters.
The final letter of 'barrel' is 'l'.
'seep' placed around 'l' is 'SLEEP'.
'and' acts as a link.
(Other definitions for sleep that I've seen before include "''... that knits up the ravell'd sleeve of care'' (Macbeth)" , "Slumber" , "Wayne _; former Royal Ballet principal dancer" , "Natural state of unconscious rest" , "Doze, nap" .)