No variety in the numbers crawling (3,5)
I believe the answer is:
all fours
'crawling' is the definition.
(thesaurus)
'no variety in the numbers' is the wordplay.
'no variety in' becomes 'all' (I can't explain this - if you can you should give a lot more credence to this answer).
'the numbers' becomes 'fours' (four is a kind of number).
'all'+'fours'='ALL-FOURS'
Can you help me to learn more?
(Other definitions for all fours that I've seen before include "Hands and feet" , "Hands and knees - crawl on them" , "Both arms and legs" , "Walking on them, one is on hands and knees" , "steady par round?" .)