Be losing track? (5)

I believe the answer is:

trail

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

'track?' is the definition.
(I know that trail is a type of track)

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for trail that I've seen before include "Drag along the ground" , "Country path; follow" , "Rough path" , "Linger behind" , "Spoor - lag behind" .)

I've seen this clue in The Globe and Mail.

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