Stroke stomach before beginning on legs (5)
I believe the answer is:
crawl
'stroke' is the definition.
(crawl is a kind of stroke)
'stomach before beginning on legs' is the wordplay.
'stomach' becomes 'craw' (craw is a kind of stomach).
'before beginning on legs' becomes 'l' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'craw'+'l'='CRAWL'
Can you help me to learn more?
(Other definitions for crawl that I've seen before include "be overrun" , "This can take you quickly through water" , "Move as snakes do, or on hands and knees" , "making slow progress" , "Slow advance" .)