Crossword Genius

Move ahead before second eleven gradually gain more impetus (3,2,5)

Ross

I believe the answer is:

get up steam

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'gradually gain more impetus' is the definition.
I know nothing about this answer so I can't tell whether this works.

'move ahead before second eleven' is the wordplay.
'move ahead' becomes 'getup' (getting up is a kind of moving. I am not sure about the 'ahead' bit.).
'before' says to put letters next to each other.
'second' becomes 's' (common abbreviation).
'eleven' becomes 'team' (eleven or XI can mean a football team).
'getup'+'s'+'team'='GET UP STEAM'

Can you help me to learn more?

(Other definitions for get up steam that I've seen before include "become excited" , "Gain more impetus in moving forward" .)

I've seen this clue in The Telegraph.
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