the TB-303 doesn’t have a CV in, unless you’ve had a Devilfish mod or a Kenton retrofit.
I use my Devilfish all the time with my A4, got the MIDI Thru set to Sync 24 (all rolands use that) to have it in time,
I could use an A4 track to sequence the 303, but that defeats the whole purpose of a 303! it’s the sequencer along with a couple of things that make it! 