Tosses in a turgid offhand prècis … finally (4)
I believe the answer is:
adds
'tosses in' is the definition.
(I've seen this in another clue)
'a turgid offhand precis finally' is the wordplay.
'finally' says to take the final letters.
The last letters of 'turgid offhand precis' are 'dds'.
'a'+'dds'='ADDS'
(Other definitions for adds that I've seen before include "Aggregates or makes further remark" , "Does summer job" , "Aggregates or appends" , "Calculates the sum" , "Counts" .)