Some obtain an estimate that’s most foolish (7)
I believe the answer is:
inanest
'most foolish' is the definition.
('inane' can be similar in meaning to 'foolish')
'some obtain an estimate' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'INANEST' is hidden within 'obtain an estimate'.
'that's' is the link.
(Other definitions for inanest that I've seen before include "Exhibiting minimal sense" , "Most cuckoo" , "Most silly" , "Most stupid" , "most senseless" .)