I wasn't able to start this until yesterday and have now ground to a halt. I have a full grid apart from the bottom row, the symbol and the jumbled answer but can't see the stages of the career. I suspext (prpbably mistakenly) that the character's name is entered in the bottom row and given the theme the three sets of 6 letters go up, across and then down. Any hints/heavy nudges would be welcome.
AP, your thinking (from 'I suspect...) is perfectly correct. If you tackle it in the order you've suggested - going up, across, down, you will follow the character and his 'career'.
Having just returned from the rain forest, cloud forest and latterly the Galapagos to wall to wall rain at home, this was a pleasant diversion from the downpour. Thank you, Ifor.
(I particularly like the younger Breughel’s take on the theme.)