"Define..." in context menu not working

[JohnDohe]

Hi!

My system:

MacBook
Sierra 10.12.6
FireFox 56.0b9 (64-bit)

Problem:

When I need to define a word on a webpage I right-click to select the word
and then try to left-click on the "Define..."option.

But "Loading..." appears and . . . nothing. No definition of the selected
word appears.

How to make "Define..." work?

Thanks!

PS: I do not want to upgrade either my OS to either "High Sierra" or "Mojave"
nor do I want to upgrade FireFox to the latest version becauseI like having
all my applications and extensions & addon's working, thank you!

[LIMPET235]

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