Like Leander’s efforts swimming the Hellespont? (6)

I believe the answer is:

heroic

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'like' is the definition.
Both the definition and answer are adjectives. Perhaps they are linked in a way I don't understand?

I don't understand the remainder of the clue.

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(Other definitions for heroic that I've seen before include "Very brave and noble" , "Epic" , "Gallant" , "larger than life" , "Showing no fear in the face of extreme difficulty" .)

I've seen this clue in the Evening Standard.

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