Rent four unnumbered houses, to then opt for one (5,10)
I believe the answer is:
split infinitive
'then opt for one' is the definition.
I can't judge whether this defines the answer.
'rent four unnumbered houses' is the wordplay.
'rent' becomes 'split' (rent can mean split or torn).
'four' becomes 'IV' (Roman numerals for four).
'unnumbered' becomes 'infinite' (synonyms).
'houses' means one lot of letters goes inside another.
'iv' placed within 'infinite' is 'infinitive'.
'split'+'infinitive'='SPLIT INFINITIVE'
'to' is the link.
Can you help me to learn more?
(Other definitions for split infinitive that I've seen before include "Grammatical error to many" , "To boldly go" , "structure some object to" .)