。
The little boy hugged his dog tight.
Literal
Young boy [topic-は] him [possessive-の] dog [object-を] hugged-tightly.
抱きしめる is a compound: 抱く ('embrace') + 締める ('tighten') = 'hug tightly / squeeze.' Parallel to 握りしめる = 'grip tightly.' The ~しめる suffix adds the 'tightly' nuance to hold-type verbs.