Curve in mid-March? (3)
I believe the answer is:
arc
'curve' is the definition.
(arc is a kind of curve)
'in mid-march?' is the wordplay.
'in' says the answer is hidden in the clue.
'ARC' is hidden within 'mid march'.
(Other definitions for arc that I've seen before include "Curving trajectory" , "Segment of circumference" , "be rapidly discharged" , "Curve of car" , "Don't go straight" .)