Complete departure, terribly hot and bumpy at the outset (13)
I believe the answer is:
thoroughgoing
'complete' is the definition.
('thoroughgoing' can be similar in meaning to 'complete')
'departure terribly hot and bumpy at the outset' is the wordplay.
'departure' becomes 'going' ('going' can be a synonym of 'departure').
'terribly' indicates anagramming the letters.
'and' means one lot of letters go next to another.
'bumpy' becomes 'rough' ('rough' can be similar in meaning to 'bumpy'**).
'at the outset' means one lot of letters go next to another.
'hot' anagrammed gives 'tho'.
'tho'+'rough' is 'thorough'.
'going' put after 'thorough' is 'THOROUGHGOING'.
(Other definitions for thoroughgoing that I've seen before include "to the end" , "Complete, absolute" , "Extremely meticulous" , "comprehensive" .)