The 19-year-old victim was blasted with a sawn-off shotgun in a car park after rivals lay in wait for him inside a tower block.
Mr A was among four suspects charged with murder and put on trial at the Old Bailey.
It was alleged that the victim – a member of the teenage ‘Get Money Gang’ was killed by members of rival gang ‘Dem Africans’.
Both gangs were based in neighbouring turf in Enfield and Edmonton, north London.
Mr A was accused of assisting gunman, Mr T, including by acting as a ‘doorman’ by allowing the gang access to the tower block in Edmonton.
Mr T was seen on CCTV pulling a sawn-off shotgun from a carrier bag before firing a shot at Mr Hussein, chasing him and then firing a second time.
Mr A denied murder and instructed Stuart Miller Solicitors to defend him.
Prosecutors claimed he was guilty of murder under the controversial law of joint enterprise where more than one person can be convicted of a crime if they had foresight that it was going to take place.
Mr A claimed he had no involvement in the shooting and that he had no idea that a shooting was going to take place.
He was not visible on the CCTV shown in court, the court heard.
Jurors acquitted him after a trial. Mr T was convicted of murder at a retrial.