Convenience sets out to be most approximate (7)
I believe the answer is:
loosest
'most approximate' is the definition.
Both the definition and answer are superlative adjectives. Perhaps they are linked in a way I don't understand?
'convenience sets out' is the wordplay.
'convenience' becomes 'loo' (both can mean a toilet).
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'sets' is an anagram of 'sest'.
'loo'+'sest'='LOOSEST'
'to be' acts as a link.
Can you help me to learn more?
(Other definitions for loosest that I've seen before include "most relaxed" , "most unstable" .)