Gathers yours truly has set off (5)
I believe the answer is:
meets
'gathers' is the definition.
('meet' can be a synonym of 'gather')
'yours truly has set off' is the wordplay.
'yours truly' becomes 'me' (the person who set this crossword).
'has' means one lot of letters go next to another.
'off' indicates an anagram.
'set' is an anagram of 'ets'.
'me'+'ets'='MEETS'
(Other definitions for meets that I've seen before include "Joins with" , "Gathers together" , "Comes into contact with" , "Comes across" , "sports gatherings" .)