Notes very small rhinoceros’s bottom (7)
I believe the answer is:
minutes
'notes' is the definition.
(minute is a kind of note)
'very small rhinoceros's bottom' is the wordplay.
'very small' becomes 'minute' (I've seen this before).
'bottom' says to take the final letters.
The final letter of 'rhinoceros' is 's'.
'minute'+'s'='MINUTES'
(Other definitions for minutes that I've seen before include "Records" , "Record of a meeting's decisions" , "Written account of a meeting" , "Units of time" , "Record of a meeting" .)