Deep understanding to strike left on board (7)

I believe the answer is:

rapport

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'deep understanding' is the definition.
'rapport' can be an answer for 'understanding' (I've seen this before). I'm not certain of the 'deep' bit.

'strike left on board' is the wordplay.
'strike' becomes 'rap' (synonyms).
'left on board' becomes 'port' (port is left on board a ship).
'rap'+'port'='RAPPORT'

'to' acts as a link.

Can you help me to learn more?

(Other definitions for rapport that I've seen before include "Mutual harmony and affinity" , "Sympathetic relationship" , "Emotional bond" , "Mutual sensitivity and understanding" , "Relation, connection" .)

I've seen this clue in the Sydney Morning Herald.

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