Tiny bit of lettuce stuck in dentures unfortunately — that's what happened (3,6)
I believe the answer is:
end result
'that's what happened' is the definition.
'tiny bit of lettuce stuck in dentures unfortunately' is the wordplay.
'tiny bit of' says to take the initial letters.
'stuck in' indicates putting letters inside.
'unfortunately' indicates anagramming the letters.
The first letter of 'lettuce' is 'l'.
'dentures' is an anagram of 'endresut'.
'l' put inside 'endresut' is 'END RESULT'.
(Other definitions for end result that I've seen before include "Elders run to find ultimate consequence" , "Latest" , "Final product" , "Eldest run to reach final outcome" .)