Donation by partnership firm to trust

Yes he can donate and same amount can be claimed as deduction of entire amount as expense

donations under 80 G are subject to restrictions. some are 100% and some are 50% deductible while some are deductible to 10% of the gross total income.
so you need to check under which category your trust falls. I presume that it falls under the category of 10% deduction of the gross total income. you can refer section 80G for more clarification regarding the category of your firm.

Thats about deduction from income but as an expense entire 100% amount can be claimed if donation helps in growing business

as an expense any donation is disallowed while calculating taxable income and then deduction is allowed under section 80G. subject to overall limits.
I believe he's asking from taxation point of view and not about accounting view