Referee on boundary cited Docker? (6)
I believe the answer is:
remora
'docker?' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'referee on boundary cited' is the wordplay.
I cannot really understand how this works, but
'on' could be 're' ('on' can be mean 'with reference to') and 're' is found in the answer.
The remaining letters 'mora' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for remora that I've seen before include "Slender sea fish" , "Arm roe against suckerfish" .)