Scales need some calibration (5)
I believe the answer is:
libra
'scales' is the definition.
(I have seen 'The Scales' mean 'libra' so perhaps 'scales' could also mean 'libra')
'need some calibration' is the wordplay.
'need some' indicates a hidden word (I've seen 'needing some' mean this).
'LIBRA' can be found hidden inside 'calibration'.
(Other definitions for libra that I've seen before include "Scales star sign" , "The Scales in astrology" , "Someone born between September 23 and October 22" , "Balance constellation" , "Zodiac sign of the scales" .)