Finally redeployed an old falconer (4,3,3,3)
I believe the answer is:
once and for all
'finally' is the definition.
(I've seen this before)
'redeployed an old falconer' is the wordplay.
'redeployed' is an anagram indicator (I've seen this in other clues).
'an'+'old'+'falconer'='anoldfalconer'
'anoldfalconer' is an anagram of 'ONCE AND FOR ALL'.
(Other definitions for once and for all that I've seen before include "In a conclusive way" , "how might an inclusively unique show be performed?" , "Conclusively" , "For the last time" , "Decisively" .)