Roll along clumsily? Not ruled out when short of oxygen (7)
I believe the answer is:
trundle
'roll along clumsily?' is the definition.
(to trundle along is to move clumsily)
'not ruled out when short of oxygen' is the wordplay.
I cannot quite understand how this works, but
'not' could be 'un' (I've seen this in other clues) and 'un' is located in the answer.
'when' could be 'e' (I've seen this in other clues) and 'e' is found within the answer.
This may be the basis of clue (or it may be nonsense).
(Other definitions for trundle that I've seen before include "spin?" , "slow movement" , "Move heavily, as if on wheels" , "Move slowly and awkwardly" , "Move or roll heavily" .)