Romeo gets colleague to perk up (5)
I believe the answer is:
rally
'perk up' is the definition.
(I've seen this in another clue)
'romeo gets colleague' is the wordplay.
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'gets' means one lot of letters go next to another.
'colleague' becomes 'ally' (ally can mean a colleague or associate).
'r'+'ally'='RALLY'
'to' is the link.
(Other definitions for rally that I've seen before include "Muster" , "Revive - motoring contest" , "Get better; car meet" , "(Of shares) increase after a fall" , "Mass meeting -- revive" .)