Crossword Genius

Lean pigs mucked up, seen in passing (8)

Ross

I believe the answer is:

elapsing

I'm a little stuck... Click here to teach me about this clue!

Here is my best explanation:

'passing' is the definition.
('elapse' can be a synonym of 'pass')

I don't understand the remainder of the clue.

Can you help me to learn more?