Beside this, arguably, there is some lack of application (3,5)

I believe the answer is:

the point

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'beside this arguably there' is the definition.
The definition suggests a singular noun which matches the answer.

'some lack of application' is the wordplay.
'some' becomes 'they'.
'lack of' means to remove the last letter (I've seen 'lacking' mean this (the word is incomplete or lacking)).
'application' becomes 'point' (I am not sure about this - if you are sure you should believe this answer much more).
'they' with its final letter taken off is 'the'.
'the'+'point'='THE POINT'

'is' acts as a link.

Can you help me to learn more?

I've seen this clue in the Evening Standard.

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