Credit law broken at a stroke (5)
I believe the answer is:
crawl
'a stroke' is the definition.
(I know that crawl is a type of swimming stroke)
'credit law broken' is the wordplay.
'credit' becomes 'cr' (abbreviation).
'broken' is an anagram indicator.
'law' with letters rearranged gives 'awl'.
'cr'+'awl'='CRAWL'
'at' is the link.
(Other definitions for crawl that I've seen before include "Slow advance" , "fawn" , "Move slowly (as a baby does?)" , "Progress, slow on land but fast in water" , "progress slowly" .)