It would be pleasant to free the lab mice, for a start (8)

I believe the answer is:

amicable

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'it would be pleasant' is the definition.
The definition suggests a singular noun but the answer is not.

'free the lab mice for a start' is the wordplay.
'free' indicates an anagram.
'for' is a charade indicator (letters next to each other).
'start' is a charade indicator (letters next to each other).
'lab'+'mice'='labmice'
'labmice' is an anagram of 'micable'.
'micable' after 'a' is 'AMICABLE'.

'to' is the link.

Can you help me to learn more?

(Other definitions for amicable that I've seen before include "Friendly and sociable" , "Friendly, peaceable" , "Of friendly and affable disposition" , "Civil" , "Friendly, nonthreatening" .)

I've seen this clue in the Evening Standard.

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