What does the cryptic crossword clue "Frame OK for car when travelling (4,4)" mean?

The definition is "Frame". The wordplay uses an anagram. anagram of OK + FOR + CAR = ROOF RACK; definition: "Frame" The answer is Roof rack.

Frame OK for car when travelling (4,4)

Telegraph Prize Cryptic #3000 | 21 Across | 2019-04-21 flower