Remind one young lady to be lavish (8)
I believe the answer is:
prodigal
'be lavish' is the definition.
(similar in meaning)
'remind one young lady' is the wordplay.
'remind' becomes 'prod' (prod can mean to remind someone about something).
'one' becomes 'i' (Roman numeral).
'young lady' becomes 'gal' (synonyms).
'prod'+'i'+'gal'='PRODIGAL'
'to' acts as a link.
(Other definitions for prodigal that I've seen before include "Spendthrift" , "This son got the fatted calf" , "Improvident" , "Wasting money" , "Recklessly wasteful or extravagant" .)