Second coach is a try-hard (8)
I believe the answer is:
strainer
'a try-hard' is the definition.
I can't judge whether this definition defines the answer.
'second coach' is the wordplay.
'second' becomes 's' (common abbreviation).
'coach' becomes 'trainer' (as in a sports coach).
's'+'trainer'='STRAINER'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for strainer that I've seen before include "device to catch leaves" , "to collect leaves?" , "One gathers leaves" , "who tries really hard?" , "Retrains (anag.)" .)