When collections are worth having (6)
I believe the answer is:
assets
'worth having' is the definition.
I can't judge whether this definition defines the answer.
'when collections' is the wordplay.
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'collections' becomes 'sets' (set is a kind of collection).
'as'+'sets'='ASSETS'
'are' acts as a link.
Can you help me to learn more?
(Other definitions for assets that I've seen before include "Useful or valuable things" , "Valuable resources" , "One's total goods" , "Properties that have money value" , "Stance discouraging particular action" .)