Administered a transaction before finishing breakfast (5)
I believe the answer is:
dealt
'administered' is the definition.
(I've seen this in another clue)
'a transaction before finishing breakfast' is the wordplay.
'a transaction' becomes 'deal' (a deal is a transaction or exchange).
'before' is a charade indicator (letters next to each other).
'finishing' says to take the final letters (the letter which finishes the word).
The last letter of 'breakfast' is 't'.
'deal'+'t'='DEALT'
(Other definitions for dealt that I've seen before include "Delta (anag.)" , "Carried out business" , "Handed out (cards)" , "Doled out" , "Traded" .)