Sorry to run short of fuel, somehow (6)
I believe the answer is:
rueful
'sorry' is the definition.
(synonyms)
'run short of fuel somehow' is the wordplay.
'short of' means to remove the last letter (I've seen 'shorter' mean this).
'somehow' is an anagram indicator.
'run' with its final letter taken away is 'ru'.
'fuel' is an anagram of 'eful'.
'ru'+'eful'='RUEFUL'
'to' is the link.
(Other definitions for rueful that I've seen before include "Filled with regret" , "Regretful" , "Feeling good-humoured regret" , "Feeling remorse" , "Full of regret" .)