Royal has given up lying - finally? It's true (4)
I believe the answer is:
real
'true' is the definition.
(similar in meaning)
'royal has given up lying finally?' is the wordplay.
'royal' becomes 'r' (abbreviation).
'has' says to put letters next to each other.
'given up' is a reversal indicator (in a down clue, letters go up).
'lying finally?' becomes 'lae' (I am not sure about this - if you are sure you should believe this answer much more).
'lae' reversed gives 'eal'.
'r'+'eal'='REAL'
'it's' acts as a link.
Can you help me to learn more?
(Other definitions for real that I've seen before include "very American" , "Authentic" , "True" , "Actual and tangible" , "Physically existing" .)