Signal ultimately limited at sea - that's inconvenient (3-5)
I believe the answer is:
ill-timed
'inconvenient' is the definition.
(thesaurus)
'signal ultimately limited at sea' is the wordplay.
'ultimately' indicates one should take the final letters.
'at sea' indicates anagramming the letters.
The last letter of 'signal' is 'l'.
'l'+'limited'='llimited'
'llimited' is an anagram of 'ILL-TIMED'.
'that's' is the link.
(Other definitions for ill-timed that I've seen before include "Done or occurring at an inconvenient moment" , "Badly scheduled" , "Happening at a badly chosen moment" , "Inopportune" .)