Sprinted back with speed to inform (7)
I believe the answer is:
narrate
'inform' is the definition.
(narrating is a kind of informing)
'sprinted back with speed' is the wordplay.
'sprinted' becomes 'ran' (I've seen this before).
'back' is a reversal indicator.
'with' says to put letters next to each other.
'speed' becomes 'rate' (rate is a kind of speed).
'ran' in reverse letter order is 'nar'.
'nar'+'rate'='NARRATE'
'to' is the link.
(Other definitions for narrate that I've seen before include "Give a spoken account" , "Rare ant (anag.)" , "Relate - portray" , "rehearse" , "Tell story,recount" .)