The most common and most likely answer to this crossword clue is the 8 letter word MOULDING
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More clues leading to the result MOULDING
Buddy explains!

The straight part
We know that "Fille/going off" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fille/going off = moulding.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does MOULDING mean?
MOULDING verb- To shape in or on a mold; to form into a particular shape; to give shape to.
- To guide or determine the growth or development of; influence
- To fit closely by following the contours of.
- To make a mold of or from (molten metal, for example) before casting.
- To ornament with moldings.
- To be shaped in or as if in a mold.
- To cause to become moldy; to cause mold to grow upon.
- To become moldy; to be covered or filled, in whole or in part, with a mold.
- To cover with mold or soil.
- The act or process of shaping in or on a mold, or of making molds; the art or occupation of a molder.
- Anything cast in a mold, or which appears to be so, as grooved or ornamental bars of wood or metal.
- A plane, or curved, narrow surface, either sunk or projecting, used for decoration by means of the lights and shades upon its surface and to conceal joints, especially between unlike materials.
- (woodwork) A planing machine for making moldings.
- (founding) A machine to assist in making molds for castings.
- (milling) A mill for shaping timber.
- (founding) A kind of sand containing clay, used in making molds.