Carriage in front of train — managed to have a seat (7)
I believe the answer is:
transit
'carriage' is the definition.
(I've seen this in other clues)
'front of train managed to have a seat' is the wordplay.
'front of' says to take the initial letters.
'managed' becomes 'ran' (I've seen this before).
'to have a seat' becomes 'sit' (sit down on a seat).
The initial letter of 'train' is 't'.
't'+'ran'+'sit'='TRANSIT'
'in' is the link.
(Other definitions for transit that I've seen before include "The process of going or conveying" , "carriage" , "The carrying of people etc" , "In migration" , "Passage of planet across the disc of the sun" .)