Flagship boarded by king (8)
I believe the answer is:
streamer
'flagship' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'boarded by king' is the wordplay.
I cannot quite understand how this works, but
'king' could be 'er' (abbreviation for Edward Rex, various English kings) and 'er' is found in the answer.
The remaining letters 'stream' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for streamer that I've seen before include "that hangs about now?" , "Ribbon for throwing" , "Heavy cold" , "Bit of bunting" , "awful cold?" .)