Swim before one can walk (5)
I believe the answer is:
crawl
This might be a double definition.
'swim' is the first definition.
(crawling is a kind of swimming)
'one can walk?' is the second definition.
'crawl' can be an answer for 'walk?' (thesaurus). I am unsure of the 'one can' bit.
'before' acts as a link.
Can you help me to learn more?
(Other definitions for crawl that I've seen before include "Slow advance" , "Scramble on all fours" , "fawn" , "inch" , "be overrun" .)