Incomplete cross-reference for “leak”? (7)

I believe the answer is:

seepage

'leak?' is the definition.
(thesaurus)

I cannot understand how the remainder of the clue works.

(Other definitions for seepage that I've seen before include "Slow flow of fluid" , "Ooze" , "Slow fluid loss" , "narrow escape?" , "Oozing liquid" .)

I've seen this clue in The Times.

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