Nominally you'll find a clue in central Dakar (5)
I believe the answer is:
alias
'nominally' is the definition.
Both the answer and definition are adverbs. Perhaps you can see a link between them that I can't see?
'a clue in central dakar' is the wordplay.
'clue in central dakar' becomes 'lias' (I can't justify this - if you can you should believe this answer much more).
'a'+'lias'='ALIAS'
'you'll find' is the link.
Can you help me to learn more?
(Other definitions for alias that I've seen before include "A sail (anag)" , "it may be assumed" , "Handle that isn't genuine" , "Pseudonym" , "Alternative name" .)