Longed to show a bit of panache at the grand finale (5)
I believe the answer is:
ached
'longed' is the definition.
('ache' can be a synonym of 'long')
'a bit of panache at the grand finale' is the wordplay.
'a bit of panache at' becomes 'ache' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'finale' suggests the final letters.
The last letter of 'grand' is 'd'.
'ache'+'d'='ACHED'
'to show' is the link.
Can you help me to learn more?
(Other definitions for ached that I've seen before include "Hurt" , "Had a continuous pain" , "caused discomfort" , "suffered" , "Throbbed" .)