Some loathsome manager sent round note (4)
I believe the answer is:
memo
'note' is the definition.
(a memo is a short note)
'some loathsome manager sent round' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'sent round' is a reversal indicator.
'omem' is hidden in the letters of 'loathsome manager'.
'omem' back-to-front is 'MEMO'.
(Other definitions for memo that I've seen before include "Inter-office note" , "A little something to be remembered" , "Note written as a reminder" , "Brief note, usually between co-workers" , "It will remind" .)