Search through an eternal well of alternatives (5)
I believe the answer is:
trawl
'search' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for trawl that I've seen before include "Fish by dragging bag-net along sea bed" , "search for information" , "Net dragged behind fishing boats" , "hunt" , "Fish using a towed net" .)