Interrupt a Kerryman glossing over the extent to which it's being availed of (6)
I believe the answer is:
uptake
'extent to which it's being availed of' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'interrupt a kerryman glossing over' is the wordplay.
'over' says the answer is hidden in the clue (the clue contains or goes 'over' the answer).
'UPTAKE' is hidden within 'interrupt a kerryman glossing'.
'the' is the link.
Can you help me to learn more?
(Other definitions for uptake that I've seen before include "Grasp one can be quick on" , "understanding" , "Apprehension" , "Acceptance of offer" , "Ability to understand what is meant - some are quick on it" .)