Exclusively for us, covering foot, arms and legs (3,5)
I believe the answer is:
all fours
'arms and legs' is the definition.
I can't tell whether this defines the answer.
'exclusively for us covering foot' is the wordplay.
'exclusively' becomes 'all' (I've seen this in another clue).
'for us' becomes 'ours' (I've seen this in another clue).
'covering' means one lot of letters goes inside another.
'foot' becomes 'f' (abbreviation).
'all'+'ours'='allours'
'allours' placed around 'f' is '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" , "steady par round?" , "Bear thus to make progress" .)