Understand the meaning of "Be reasonable" (3,5)

I believe the answer is:

see sense

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'be reasonable' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.

'understand the meaning' is the wordplay.
'understand' becomes 'see' (synonyms).
'the meaning' becomes 'sense' (synonyms).
'see'+'sense'='SEE SENSE'

'of' is the link.

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