It’s clear that detectives need a bit of luck (5)
I believe the answer is:
lucid
'it's clear that detectives need a bit of luck' is the definition.
'lucid' can be an answer for 'it's clear' (thesaurus). I'm unsure of the rest of the definition.
'it's clear that detectives' is the wordplay.
'it's clear' becomes 'lu' (I am not sure about this - if you are sure you should believe this answer much more).
'that detectives' becomes 'cid'.
'lu'+'cid'='LUCID'
Can you help me to learn more?
(Other definitions for lucid that I've seen before include "Quite clear" , "Transparently clear" , "Transparent" , "Bright; sane" , "Clearly expressed and altogether rational" .)