Butch physicist who worked on speed and bit of oxy (5)
I believe the answer is:
macho
'butch physicist who worked' is the definition.
'macho' can be an answer for 'butch' (I've seen this before). I'm not sure about the remainder of the definition.
'speed and bit of oxy' is the wordplay.
'speed' becomes 'mach' (I have seen 'Speed of sound ' mean 'mach' so perhaps 'speed' could also mean 'mach').
'and' means one lot of letters go next to another.
'bit of' suggests taking the first letters.
The initial letter of 'oxy' is 'o'.
'mach'+'o'='MACHO'
'on' is the link.
Can you help me to learn more?
(Other definitions for macho that I've seen before include "Jock" , "Ramboesque" , "Exaggeratedly masculine" , "Aggressively masculine" , "Excessively male" .)