Start agitation and resistance to rival getting off Jumbo (7)

I believe the answer is:

arrival

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'off jumbo' is the definition.
I can't judge whether this defines the answer.

'start agitation and resistance to rival' is the wordplay.
'start' suggests taking the first letters.
'and' means one lot of letters go next to another.
'resistance' becomes 'r' (abbreviation).
'to' is a charade indicator (letters next to each other).
The first letter of 'agitation' is 'a'.
'a'+'r'+'rival'='ARRIVAL'

'getting' is the link.

Can you help me to learn more?

(Other definitions for arrival that I've seen before include "Someone who's just come" , "Coming - comer" , "Entry" , "Advent" , "Attainment of destination" .)

I've seen this clue in the Irish Times.

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