Real mad? Cross? Take it easy! (5)
I believe the answer is:
relax
'take it easy' is the definition.
(I've seen this before)
'real mad? cross?' is the wordplay.
'mad?' indicates anagramming the letters (I've seen 'mad' mean this).
'cross?' becomes 'x' (an X is a cross).
'real' is an anagram of 'rela'.
'rela'+'x'='RELAX'
(Other definitions for relax that I've seen before include "Don't worry" , "Become less tense" , "Moderate" , "Unbend" , "Unwind, take it easy" .)