Once aboard, I reset navigation aid (5,6)

I believe the answer is:

radio beacon

I'm a little stuck... Click here to teach me more about this clue!

'navigation aid' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.

'once aboard i reset' is the wordplay.
'reset' is an anagram indicator.
'once'+'aboard'+'i'='onceaboardi'
'onceaboardi' with letters rearranged gives 'RADIO-BEACON'.

Can you help me to learn more?

(Other definitions for radio beacon that I've seen before include "transmitter used for navigation" , "signalling station" , "[SIGNAL] apparatus" .)

I've seen this clue in The Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.