Likelihood of fatal dose being taken by detective? (4)
I believe the answer is:
odds
'likelihood' is the definition.
(what are the odds?)
'fatal dose being taken by detective?' is the wordplay.
'fatal dose' becomes 'OD' (overdose).
'being taken by' says to put letters next to each other.
'detective?' becomes 'DS' (detective sergeant).
'od'+'ds'='ODDS'
'of' acts as a link.
(Other definitions for odds that I've seen before include "Bookies give them" , "Things not even" , "Betting figures" , "(In betting) chances" , "Estimate of likelihood" .)