hi there!! first of all i think you did a good job choice. i think most of us wont get rich with physio, but to help people and see them imporving is better anyway.
to your case: when you pronate your foot you can feel a tendon right behind your lat. malleolus, its the peroneus longus tendon. is it snapping when you are activeley pronating or against resistance? if yes try to fix it with a little pressure and see what happens. i asume you had a inversion trauma. in this case often peroneal tendon sheath gets damaged, which isnt a real problem.
try to work a lot on instable (wobble bord etc) an see if the problem improve.
also if the post. calcaneofib. lig. is damaged it can cause this snapping. but if isolated damaged (or not reconstructed during surgery) it often causes no real joint laxity.
anyhow, try a lot of stabilizing exercises and strengthening. good luck!!