Run into Romeo one morning (3)
I believe the answer is:
ram
'run into' is the definition.
(I've seen this in another clue)
'romeo one morning' is the wordplay.
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'one morning' becomes 'am' (as in 12:00 AM).
'r'+'am'='RAM'
(Other definitions for ram that I've seen before include "With violence" , "'Computer memory, initially (3)'" , "Thrust" , "Prepare to raid" , "Computers need it to operate" .)