Head of science to take up chair (4)
I believe the answer is:
seat
'chair' is the definition.
(something to sit on)
'head of science to take up' is the wordplay.
'head of' indicates taking the first letters.
'to' means one lot of letters go next to another.
'take up' becomes 'eat' (eating is a kind of taking. I am not sure about the 'up' bit.).
The initial letter of 'science' is 's'.
's'+'eat'='SEAT'
Can you help me to learn more?
(Other definitions for seat that I've seen before include "Chair, bench, saddle, etc" , "Parliamentary constituency" , "Sitting place" , "A manner of sitting on horse" , "Constituency; location" .)