Try reading out opening bits of "Secret Agent" (5)
I believe the answer is:
essay
'try' is the definition.
(essay can mean to try or attempt something)
'out opening bits of secret agent' is the wordplay.
I cannot quite understand how this works, but
'secret' could be 'ess' (I have seen 'top secret' mean 'ess' so perhaps 'secret' could also mean 'ess') and 'ess' is located in the answer.
The remaining letters 'ay' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'reading' acts as a link.
(Other definitions for essay that I've seen before include "Make an effort to write one" , "Attempt - piece of writing" , "Try; dissertation" , "Attempt; written piece" , "Try; short written work" .)