What does the cryptic crossword clue "After exercise bring back fish and a sort of butter (6)" mean?

The wordplay uses a reversal. PE (synonym="exercise") + TUNA (reversal="TUNA") = PEANUT The answer is PEANUT.

After exercise bring back fish and a sort of butter (6)

Guardian Cryptic #29495 | 25 Across | 2024-09-23 flower