Unlimited ambition shown by lieutenant firstly on English ship (7)

I believe the answer is:

endless

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'unlimited' is the definition.
(thesaurus)

'ambition shown by lieutenant firstly on english ship' is the wordplay.
'ambition' becomes 'end' ('end' can mean a goal or purpose).
'shown by' says to put letters next to each other.
'firstly' suggests taking the first letters.
'on english' becomes 'e' (abbreviation. I am not sure about the 'on' bit.).
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
The first letter of 'lieutenant' is 'l'.
'end'+'l'+'e'+'ss'='ENDLESS'

Can you help me to learn more?

(Other definitions for endless that I've seen before include "permanent" , "Potentially boring" , "Unceasing" , "Infinite, perpetual" , "'Eternal, perpetual (7)'" .)

I've seen this clue in The Telegraph.

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