Fish finger's last to be consumed by solicitor (5)
I believe the answer is:
trout
'fish' is the definition.
(I know that trout is a type of fish)
'finger's last to be consumed by solicitor' is the wordplay.
'last' indicates one should take the final letters.
'to be consumed by' indicates putting letters inside (inserted letters get consumed).
'solicitor' becomes 'tout' (someone who solicits business).
The last letter of 'finger' is 'r'.
'r' inserted inside 'tout' is 'TROUT'.
(Other definitions for trout that I've seen before include "Oily fish" , "Tickled fish?" , "Commonly caught fish" , "Tasty fish, brown or rainbow" , "Fish - old harridan" .)