Numbers one estimated were most curious (7)
I believe the answer is:
nosiest
'most curious' is the definition.
('nosy' can be similar in meaning to 'curious')
'numbers one estimated' is the wordplay.
'numbers' becomes 'nos' ('no' is an abbreviation for number).
'one' becomes 'i' (Roman numeral).
'estimated' becomes 'est' (abbreviation).
'nos'+'i'+'est'='NOSIEST'
'were' acts as a link.
(Other definitions for nosiest that I've seen before include "Most inquisitive" , "Most snoopy" , "One sits (anag)" , "Most prying" , "Most offensively curious" .)