Shorten a crossing (7)
I believe the answer is:
abridge
'shorten' is the definition.
(synonyms)
'a crossing' is the wordplay.
I cannot quite see how this works, but
'a' is within the answer.
The remaining letters 'bridge' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for abridge that I've seen before include "Abbreviate, contract" , "Shorten (a literary work)" , "Condense, summarise" , "Shorten (eg, text)" , "prune?" .)