Mo Salah's header caught by home team's no. 1, a six-footer (7)
I believe the answer is:
instant
'mo' is the definition.
(both can mean a short period of time)
'salah's header caught by home team's no 1 a six-footer' is the wordplay.
'header' suggests taking the first letters (in a down clue, the letter at the top of the word).
'caught by' means one lot of letters goes inside another.
'home' becomes 'in' ('he's home' can mean 'he's in').
'team's no 1' becomes 't' (1st letter of 'team').
'a six footer' becomes 'ant' (an ant has six feet).
The initial letter of 'salah' is 's'.
'in'+'t'='int'
's' inserted inside 'int' is 'inst'.
'inst'+'ant'='INSTANT'
(Other definitions for instant that I've seen before include "Not detailed" , "Sort of coffee" , "Jiffy" , "Without delay - short time" , "Short moment" .)