Some Glaswegian tycoon – Mr. Big? (5)
I believe the answer is:
giant
'big?' is the definition.
(similar in meaning)
'some glaswegian tycoon mr' is the wordplay.
'some' indicates a hidden word (some parts of the word are used).
'GIANT' is hidden within 'glaswegian tycoon mr'.
(Other definitions for giant that I've seen before include "Superhuman being" , "Very big person" , "Monster" , "Huge; James Dean film" , "Colossus" .)