Most restrained in very noisy trial (7)
I believe the answer is:
softest
'most restrained' is the definition.
Both the definition and answer are superlative adjectives. Perhaps you can see a link between them that I don't see?
'very noisy trial' is the wordplay.
'very' becomes 'so' (I've seen this in other clues).
'noisy' becomes 'f'.
'trial' becomes 'test' (synonyms).
'so'+'f'+'test'='SOFTEST'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for softest that I've seen before include "Least hard or rough" , "Lowest in volume" , "Most delicate or most lenient" , "most weak" .)