Regular returned holding right cheek (5)
I believe the answer is:
nerve
'cheek' is the definition.
(I've seen this before)
'regular returned holding right' is the wordplay.
'regular' becomes 'even' ('even' can be similar in meaning to 'regular').
'returned' says the letters should be written in reverse.
'holding' means one lot of letters goes inside another.
'right' becomes 'r' (common abbreviation).
'even' written backwards gives 'neve'.
'neve' placed around 'r' is 'NERVE'.
(Other definitions for nerve that I've seen before include "that may be attached to optic?" , "Cool courage" , "Bundle of fibres in the body (5)" , "Audacity (informal)" , "Bundle of fibres < in face" .)