Adjustment made in time, spring back (4,6)
I believe the answer is:
leap second
'adjustment made in time' is the definition.
(second added to Coordinated Universal Time)
'spring back' is the wordplay.
'spring' becomes 'leap' (synonyms).
'back' becomes 'second' (synonyms).
'leap'+'second'='LEAP SECOND'
(Other definitions for leap second that I've seen before include "Calendar adjustment" , "Time-keeping adjustment" , "Time correction" , "brief period of extra time" .)