In favour of hosting University rowing crew, perhaps (4)
I believe the answer is:
four
'rowing crew perhaps' is the definition.
I can't tell whether this defines the answer.
'in favour of hosting university' is the wordplay.
'in favour of' becomes 'for' (being for a particular cause).
'hosting' means one lot of letters goes inside another (inserted letters are welcomed in or hosted).
'university' becomes 'U' (abbreviation as in UMass).
'for' placed around 'u' is 'FOUR'.
Can you help me to learn more?
(Other definitions for four that I've seen before include "Number of players in a doubles game" , "IV in Roman numerals" , "Number in quartet" , "Set of bridge players?" , "Figure" .)