Resolute hawk going after seconds (5)
I believe the answer is:
stout
'resolute' is the definition.
(similar in meaning)
'hawk going after seconds' is the wordplay.
'hawk' becomes 'tout' (both can mean to sell something).
'going after' says to put letters next to each other.
'seconds' becomes 's' (abbreviation).
'tout' after 's' is 'STOUT'.
(Other definitions for stout that I've seen before include "Inured to fatigue and hardship" , "Rather fat; determined" , "drinks?" , "Dark ale" , "Overweight; porter" .)