Obstruct vehicle on rails with short fuse (7)
I believe the answer is:
trammel
'obstruct' is the definition.
(thesaurus)
'vehicle on rails with short fuse' is the wordplay.
'vehicle on rails' becomes 'tram' (I've seen this before).
'with' means one lot of letters go next to another.
'short' means to remove the last letter.
'fuse' becomes 'meld' (synonyms).
'meld' with its final letter taken away is 'mel'.
'tram'+'mel'='TRAMMEL'
(Other definitions for trammel that I've seen before include "Limit, hamper" , "Constrain, impede" , "Hobble" , "Three-layered fishing net - melt ram (anag)" , "Place limits on" .)