Indication you need a sling after fracture (6)
I believe the answer is:
signal
'indication' is the definition.
(I've seen this before)
'a sling after fracture' is the wordplay.
'after fracture' is an anagram indicator (I've seen this in other clues).
'a'+'sling'='asling'
'asling' is an anagram of 'SIGNAL'.
'you need' is the link.
(Other definitions for signal that I've seen before include "(Traffic) light" , "Nonverbal action or gesture that encodes a message" , "Gesture encoding a message" , "Non-verbal action with an encoded message" , "(Railway) light" .)