Certainly tricky, these puzzles ultimately (3)
I believe the answer is:
yes
'certainly' is the definition.
(both can be used to answer in the affirmative)
'tricky these puzzles ultimately' is the wordplay.
'ultimately' indicates one should take the final letters.
The final letters of 'tricky these puzzles' are 'YES'.
(Other definitions for yes that I've seen before include "One response to "will you marry me?"" , "Certainly!" , "Positive response" , "Pro vote" , "Word of affirmation" .)