Being resolute, many should finish strongly (7)
I believe the answer is:
doughty
'being resolute' is the definition.
(I've seen this before)
'many should finish strongly' is the wordplay.
'many' becomes 'D' (Roman numeral for t00).
'should' becomes 'ought' (synonyms).
'finish' suggests the final letters.
The last letter of 'strongly' is 'y'.
'd'+'ought'+'y'='DOUGHTY'
(Other definitions for doughty that I've seen before include "Brave, resolute (arch.)" , "Stout-hearted, valiant" , "Fearless" .)