Mark redeployed as organisation's first prophet (10)
I believe the answer is:
apostrophe
'mark' is the definition.
(punctuation mark)
'redeployed as organisation's first prophet' is the wordplay.
'redeployed' indicates anagramming the letters (I've seen this in other clues).
'organisation's first' becomes 'o' (1st letter of 'organisation').
'as'+'o'+'prophet'='asoprophet'
'asoprophet' is an anagram of 'APOSTROPHE'.
(Other definitions for apostrophe that I've seen before include "address?" , "Mark showing omission of letters" , "Single quote mark" , "Often misplaced punctuation mark" , "detail of punctuation" .)