Lab gear prepared for school subject (7)
I believe the answer is:
algebra
'school subject' is the definition.
(branch of mathematics)
'lab gear prepared' is the wordplay.
'prepared' indicates anagramming the letters.
'lab'+'gear'='labgear'
'labgear' is an anagram of 'ALGEBRA'.
'for' is the link.
(Other definitions for algebra that I've seen before include "letters here set out the problem" , "Form of maths" , "Branch of generalised arithmetic" , "branch of learning" , "for study in class" .)