'Restrained'? Sadly, I mess about (10)
I believe the answer is:
abstemious
''restrained'?' is the definition.
(I've seen this before)
'sadly i mess about' is the wordplay.
'sadly' indicates anagramming the letters.
'i'+'mess'+'about'='imessabout'
'imessabout' is an anagram of 'ABSTEMIOUS'.
(Other definitions for abstemious that I've seen before include "Restrained in one's appetites" , "in a way that's restrained" , "refraining from excess" , "not eating or drinking a lot" , "Temperate" .)