Spell it back to me (4)
I believe the answer is:
time
'spell' is the definition.
(thesaurus)
'it back to me' is the wordplay.
'back' says the letters should be written in reverse.
'it' in reverse letter order is 'ti'.
'ti'+'me'='TIME'
(Other definitions for time that I've seen before include "Era" , "See 12" , "Hours clocked up?" , "Prison sentence (colloq.)" , "Measure of duration" .)