Singular couple adopting little darling (7)
I believe the answer is:
sweetie
'darling' is the definition.
(I've seen this before)
'singular couple adopting little' is the wordplay.
I cannot quite see how this works, but
'singular' could be 's' (abbreviation sometimes used in dictionaries) and 's' is present in the answer.
'couple' could be 'tie' (both can mean to join) and 'tie' is found in the answer.
'little' could be 'wee' (similar in meaning) and 'wee' is found in the answer.
No letters remain.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for sweetie that I've seen before include "treasure?" , "dear" , "Term of endearment" , "Darling" , "Maybe boyfriend" .)