Wicked Caliphs incarcerate Yankee corporal (8)
I believe the answer is:
physical
'corporal' is the definition.
(similar in meaning)
'wicked caliphs incarcerate yankee' is the wordplay.
'wicked' indicates an anagram.
'incarcerate' means one lot of letters goes inside another.
'yankee' becomes 'Y' (phonetic alphabet: alpha, bravo, charlie etc.).
'caliphs' with letters rearranged gives 'phsical'.
'phsical' placed around 'y' is 'PHYSICAL'.
(Other definitions for physical that I've seen before include "Examination - of the body" , "Medical check" , "Requiring bodily effort" , "Check-up" , "Involving bodily contact" .)