Retreat in theory periodically affords virtue (7)
I believe the answer is:
honesty
'virtue' is the definition.
(I've seen this before)
'retreat in theory periodically' is the wordplay.
'retreat' becomes 'nest' (nest is a kind of retreat).
'in' is an insertion indicator.
'periodically' means one should take alternating letters (letters must be selected 'every so often').
The alternate letters of 'theory' are 'hoy'.
'nest' going inside 'hoy' is 'HONESTY'.
'affords' is the link.
This may not be right. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for honesty that I've seen before include "truth" , "Probity; plant" , "A virtue" , "It's said to be the best policy" , "Plant; truthfulness" .)
