Gateways from harbour too short (7)
I believe the answer is:
portals
'gateways' is the definition.
(I've seen this in another clue)
'harbour too short' is the wordplay.
'harbour' becomes 'port' (I've seen this before).
'too' becomes 'also' (synonyms).
'short' means to remove the last letter.
'also' with its final letter taken off is 'als'.
'port'+'als'='PORTALS'
'from' is the link.
(Other definitions for portals that I've seen before include "Grand, imposing entrances" , "gates" , "Imposing gateways" .)