Something like a trainer also boarding ship on promontory (8)

I believe the answer is:

sandshoe

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'something like a trainer' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.

'also boarding ship on promontory' is the wordplay.
'also' becomes 'and' (both can mean in addition).
'boarding' is an insertion indicator.
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'on promontory' becomes 'hoe' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'and' placed inside 'ss' is 'sands'.
'sands'+'hoe'='SANDSHOE'

Can you help me to learn more?

(Other definitions for sandshoe that I've seen before include "footwear" , "Plimsoll" .)

I've seen this clue in The Guardian.

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