Less friendly, showing back to monarch once (7)
I believe the answer is:
sterner
'less friendly' is the definition.
I can't judge whether this definition defines the answer.
'back to monarch once' is the wordplay.
'back' becomes 'stern' (stern means the back of a boat).
'to monarch once' becomes 'ER' (Elizabeth Regina, ie Queen Elizabeth).
'stern'+'er'='STERNER'
'showing' is the link.
Can you help me to learn more?
(Other definitions for sterner that I've seen before include "Less easy-going" , "More grimly serious" , "Renters of more strict sort" , "More demanding" , "more inflexible anyway" .)