Stomach large? Move slowly (5)
I believe the answer is:
crawl
'move slowly' is the definition.
(I've seen this before)
'stomach large?' is the wordplay.
'stomach' becomes 'craw' (craw is a kind of stomach).
'large?' becomes 'L' (eg in clothes sizes).
'craw'+'l'='CRAWL'
(Other definitions for crawl that I've seen before include "Way of swimming" , "fawn" , "Baby-like advance" , "Grovel" , "Scramble on all fours" .)