Behave without reserve and wonder, alone - this messy? (3,4,4,4)
I believe the answer is:
let ones hair down
'behave without reserve' is the definition.
I know nothing about this answer so I can't judge whether this works.
'wonder alone this messy?' is the wordplay.
'messy?' indicates an anagram (I've seen 'messy' mean this).
'wonder'+'alone'+'this'='wonderalonethis'
'wonderalonethis' is an anagram of 'LET ONES HAIR DOWN'.
'and' is the link.
Can you help me to learn more?
(Other definitions for let ones hair down that I've seen before include "have a lot of fun" , "act without reserve" , "Be a disgrace to Barnet" , "Make whoopee" , "party" .)