What does the cryptic crossword clue "Greatest striker, marker after shirt, say? (3,6)" mean?

The wordplay uses a charade (building blocks). TOP (synonym="shirt, say") + SCORER (synonym="marker") = TOPSCORER The answer is TOPSCORER.

Greatest striker, marker after shirt, say? (3,6)

Guardian Cryptic #29273 | 16 Down | 2024-01-08 flower