Silly electronic currency units rising retrospectively (7)
I believe the answer is:
puerile
'silly' is the definition.
(I've seen this before)
'electronic currency units rising retrospectively' is the wordplay.
'electronic' becomes 'e' (as in e-mail or e-books).
'currency units' becomes 'lire' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'rising' becomes 'up' (similar in meaning).
'retrospectively' is a reversal indicator.
'e'+'lire'+'up'='elireup'
'elireup' backwards is 'PUERILE'.
Can you help me to learn more?
(Other definitions for puerile that I've seen before include "Childish, silly, trivial" , "Childish, immature" , "Babyish" , "Childishly silly" , "Childishly stupid" .)