Sensible man with cold gets into bed (8)
I believe the answer is:
balanced
'sensible' is the definition.
(thesaurus)
'man with cold gets into bed' is the wordplay.
'man' becomes 'alan' ().
'with' means one lot of letters go next to another.
'cold' becomes 'c' (eg on taps).
'gets into' indicates putting letters inside.
'alan'+'c'='alanc'
'alanc' inserted into 'bed' is 'BALANCED'.
(Other definitions for balanced that I've seen before include "Composed - unbiased" , "Having weight equally distributed" , "Auntie is supposedly" , "Poised, held in equilibrium" , "In a state of equilibrium" .)