解忧 is a separable verb (离合词) meaning 'to relieve worries or sorrows'. The verb 解 and object 忧 can be split: insert 了, 过, a duration, or a measure word between them, e.g. 解了半天的忧 (spent half a day relieving worries). You can also use it as a fixed phrase in 解忧杂货店 (The Solitary Gourmet-like novel title). It's a literary or semi-literary expression, common in written language and elegant speech.