Chemical I had got on account (4)
I believe the answer is:
acid
'chemical' is the definition.
(thesaurus)
'i had got on account' is the wordplay.
'had got' becomes 'd' (I can't justify this - if you can you should give a lot more credence to this answer).
'on' means one lot of letters go next to another.
'account' becomes 'ac' (abbreviation for account).
'i'+'d'='id'
'id' after 'ac' is 'ACID'.
Can you help me to learn more?
(Other definitions for acid that I've seen before include "Polluted precipitation" , "Biting - tart" , "Bitter - drug" , "- - -drop, sweet" , "scathing" .)