Vehicle used for a mid-March day out (4)
I believe the answer is:
dray
'vehicle' is the definition.
(type of cart)
'a mid-march day out' is the wordplay.
'a mid' says to take the centre.
'out' means one lot of letters goes inside another.
The central letter of 'march' is 'r'.
'r' put inside 'day' is 'DRAY'.
'used for' is the link.
(Other definitions for dray that I've seen before include "Delivery cart" , "Cart for carrying heavy goods" , "Brewery wagon" , "delivery vehicle" , "Low truck" .)