Take a lower position, note, aboard boat (5)
I believe the answer is:
kneel
'take a lower position' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'note aboard boat' is the wordplay.
'note' becomes 'n' (abbreviation).
'aboard' indicates putting letters inside.
'boat' becomes 'keel' (I've seen this before).
'n' inserted within 'keel' is 'KNEEL'.
Can you help me to learn more?
(Other definitions for kneel that I've seen before include "Show respect" , "Prepare to pray?" , "Get down to be knighted" , "prepare for dubbing?" , "Adopt proposing pose" .)