Yawn during yoga, perhaps (4)
I believe the answer is:
gape
'yawn' is the definition.
(synonyms)
'during yoga perhaps' is the wordplay.
'during' indicates the answer is hidden within the clue.
'GAPE' can be found hidden inside 'yoga perhaps'.
(Other definitions for gape that I've seen before include "Look in amazement or stupidity" , "Failure to meet" , "Hang wide open" , "Appear amazed" , "Look at with wide-open mouth" .)