Crossword Genius

Cast net worthwhile to fold (5,2,3,5)

Ross

I believe the answer is:

throw in the towel

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

'fold' is the definition.
Although both the answer and definition are verbs in their base form, I cannot understand how they can define each other.

'cast net worthwhile to' is the wordplay.
'cast' is an anagram indicator (letters are dispersed or cast around).
'net'+'worthwhile'+'to'='networthwhileto'
'networthwhileto' anagrammed gives 'THROW IN THE TOWEL'.

Can you help me to learn more?

(Other definitions for throw in the towel that I've seen before include "admit defeat" , "Cave in" , "Give oneself up" , "Make a concession" , "damp condition suggests one might?" .)

I've seen this clue in The Daily Express.
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