Thorn puts Romeo in a predicament (7)
I believe the answer is:
prickle
'thorn' is the definition.
(synonyms)
'romeo in a predicament' is the wordplay.
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'in' means one lot of letters goes inside another.
'a predicament' becomes 'pickle' (I've seen this in another clue).
'r' placed within 'pickle' is 'PRICKLE'.
'puts' is the link.
(Other definitions for prickle that I've seen before include "Small thorn" , "sharp point" , "Spine, thorn" , "Part of a burr or a hedgehog" , "Short spine" .)